Designing Buildings - User contributions [en]

Noise at Work Assessment

2020-02-10T17:32:24Z

ParkerJonesAcoustics:

= The Control of Noise at Work Regulations =

The ‘Control of Noise at Work Regulations 2005’ (‘the NAW Regulations’) sets out the legal requirements in respect of protecting employees against risks to their health and safety arising from exposure to noise whilst at work. The aim of the NAW Regulations is to protect workers from suffering long term hearing damage and tinnitus as a result of prolonged exposure to high noise levels in the workplace.

== What must an employer do? ==

The NAW Regulations apply to all workplaces and mean that employers are legally obliged to risk assess the exposure of their employees’ exposure to noise within the working environment. The employer must employ appropriate control measures to reduce noise exposure where necessary.

Regulation 5 of the NAW Regulations states that a detailed Noise at Work Risk Assessment (the purpose of this document) must be undertaken if an employee is likely to be exposed to noise at or above lower exposure action values. This may occur if a workplace is considered to be noisier than everyday life.

== Noise Exposure Action Values/Limits ==

In accordance with Regulation 4 of the NAW Regulations, a set of noise exposure action values are set which relate to the average levels of noise exposure over a working day or week, and the peak sound pressure exposure to which employees are exposed to in a working day. In summary:

• ‘exposure action values’ are the levels of exposure to noise at which employees can be exposed to, but employers are required to take certain actions to mitigate this risk, including the provision of hearing protection; and 
• ‘exposure limit values’ are the levels of noise exposure at which an employee must not be exposed to, after taking into account the noise reduction provided by personal hearing protection.

As per Regulation 4, the following exposure action and limit values are defined:

Table 1 – Definition of the exposure action and limit values

{|
|width="33%"| Action Level
|width="33%"| Threshold Values
|width="33%"| Actions Required if Thresholds Exceeded
|-
| Lower Exposure Action Value(LEAV)
|
· a daily personal exposure level (LEP,d)1 of 80 dB(A).

· a peak sound pressure level (LCPeak) of 135 dB(C).

(these limits do not account for hearing protection)
|
In the first instance, the employer should explore other methods of reducing noise levels to as low a level as is reasonably practicable. If the LEAV is still exceeded, then hearing protection is recommended and the employer must provide personal hearing protectors upon the request of any employee in this exposure category (though it must not be compulsory for the employee to wear them unless they are in a designated Hearing Protection Zone (HPZ).

The employer must also provide ‘information, instruction, and training’ to employees who are exposed to above the LEAV.
|-
| Upper Exposure Action Value(UEAV)
|
· a daily personal exposure level (LEP,d)1 of 85 dB(A).

· a peak sound pressure level (LCPeak) of 137 dB(C).

(these limits do not account for hearing protection)
| The employer shall reduce exposure to as low a level as is reasonably practicable by establishing and implementing a programme of organisational and technical measures, excluding the provision of personal hearing protectors, which is appropriate to the activity (see following subsections).If the UEAV is still exceeded, then hearing protection is compulsory to employees in this exposure category and must be supplied by the employer. If a particular area is above the UEAV, then this area must be designated as a HPZ. The employers must ensure that affected employees or employees entering the HPZ use hearing protection, who also have a duty to protect themselves.
|-
| Exposure Limit Value (ELV)
|
- a daily personal exposure level (LEP,d)1 of 87 dB(A).

· a peak sound pressure level (LCPeak) of 140 dB(C).

(the effect of personal hearing protection is accounted for in these limits)
|
Employees must not be permitted to be exposed above the exposure limits (after accounting for the noise reduction provided by personal hearing protection).

Action must be taken immediately to reduce exposure if this limit has been exceeded. The employer must review the programme of control measures, considering the technical and organisational controls, the adequacy of any hearing protection supplied and systems in place that ensures noise-control measures and hearing protection are properly used and maintained.
|}

{|
|width="100%"|
1 These limits can also apply to a weekly personal exposure level (LEP,w)

2 It may be necessary to conduct ongoing health surveillance for the exceedance of the LEAV and UEAV.
|}

== What do these action values mean? How do I mitigate noise? ==

In summary, if the noise exposure action values are exceeded then the employer may be required to

* reduce the noise exposure that produces these risks to as low a level as is reasonably practicable by either
** reducing noise at source, i.e. by using quieter equipment, a different process, engineering controls, etc.;
** reducing noise levels in the facility, i.e. through sound absorption, keeping noisy machinery away from quieter areas, screens, barriers, or enclosures; and/or
** implementing organisational measures which reduce the length of time that employees are exposed to noise, i.e. turning off equipment when not in use, introducing job rotation so employees are doing a mixture of noise and quiet tasks rather than spending all day working with high noise level equipment;
* provide employees with hearing protection if the noise exposure cannot be reduced enough by the aforementioned measures and the noise levels remain above the exposure action values;
* provide employees with information, instruction, and training on noise in the workplace; and
* carry out health surveillance where there is a risk because of exposure to loud noise.

Paragraph 66 of Regulation 6 of the NAW Regulations indicates that the employer should generally be seeking to reduce the risk of noise exposure irrespective of whether any exposure action values are exceeded. It may also be necessary to carry out ongoing reviews to the risk assessment at set periods, or when circumstances change.

=== Organisational and Technical Measures of Noise Reduction ===

Regulation 6 of the NAW Regulations indicates that “the employer shall ensure that risk from the exposure of his employees to noise is either eliminated at source or, where this is not reasonably practicable, reduced to as low a level as is reasonably practicable….. If any employee is likely to be exposed to noise at or above an upper exposure action value, the employer shall reduce exposure to as low a level as is reasonably practicable by establishing and implementing a programme of organisational and technical measures, excluding the provision of personal hearing protectors, which is appropriate to the activity.” The table below provides examples of such measures.

Table 2: Methods of controlling noise through organisational and technical measures

{|
|width="50%"| Action
|width="50%"| Example Measures
|-
| Reduce noise levels at source
|
* Sourcing quieter alternative equipment.
* Using a different quieter working process that achieves the same production outcome.
* Implement a maintenance programme to ensure that noise levels are not significantly raised from poorly maintained and old equipment.
* Apply noise silencing or vibration dampening parts to existing equipment.
* Using anti-vibration mounts to isolate the equipment from the structure to reduce structure-borne noise throughout a building.
* Attaching silencers to noisy air or gas stream inlets and exhausts.
* Fitting a noise enclosure around the machine (or the noisy part of a machine).
* Using active noise control systems around equipment that are particularly noisy at low frequency.
|-
| Reduce noise propagation throughout the workplace
|
* Placing noise equipment in an area with fewer employees and therefore limiting exposure to workers who are not directly operating this equipment.
* Increasing the distance between the source of noise and the operator/other works, which could be achieved by a remote control panel in some cases.
* Directing the noisiest parts of the equipment (i.e. the exhaust of a compressed air system) away from the working area.
* Using screens and barriers between the sound source and people, to reduce direct sound.
* Providing a ‘noise haven’ for employees, including operators, where controlling noise levels at source would be difficult.
* Providing rest facilities where the level of noise exposure is low.
* Reducing the ‘reverberation time’ in the building by adding acoustically absorbent material, either retrofitting acoustic panelling/suspended baffles or by using absorbent surface finishes (such as ceiling tiles and perforated metal roof liners).
|-
| Organisational controls
|
* Only operating equipment when strictly necessary and not leaving noisy equipment to idle.
* Reducing the number of employees working in noisy areas.
* Introducing job rotation so employees are doing a mixture of noise and quiet tasks rather than spending all day working with high noise level equipment.
* Training employees on how to reduce their risk to noise exposure, and potentially developing in-house skills noise control, to ensure that workers are able to identify when equipment is producing louder than usual noise levels and how they might be able to reduce this.
* Generally limiting the duration and intensity of exposure to noise, and having appropriate work schedules with adequate rest periods.
|}

=== Personal Hearing Protection ===

After the measures with Regulation 6 (summarised in the previous subsection) have been explored, the next step is to consider providing personal hearing protection.

Regulation 7 of the NAW Regulations indicate that hearing protection is compulsory for employees exposed to levels above the upper exposure action value (UEAV), though this is not compulsory during the quieter times of the day or if the employee is in a quiet area. It is also compulsory for any employee entering a Hearing Protection Zone (HPZ).

Hearing protection is not compulsory for employees exposed to levels below the UEAV. It is not beneficial to enforce employees to wear hearing protection when not necessary, as this can lead to isolation, decreased communication, uncomfortable working conditions and a decreased ability to hear alarms and sirens.

It is also not strictly beneficial to use hearing protectors which overprotect, for the reasons above. The main aim of hearing protection is to reduce noise levels at the ear to below at least the UEAV (85 dB(A)), but they should be avoided if they reduce noise levels to below 70 dB(A).

The table below shows the ‘single number rating’ (SNR) protection factor that is likely to be suitable for different levels of noise. The SNR value is typically stated with the hearing protection device. This is based upon the information in the NAW Regulations, and in BS EN 458:2004: Hearing protectors.

Table 3: Required protection factors for hearing protection

{|
|width="50%"| A-Weighted Noise Level (dB(A)) 1
|width="50%"| Select a protector with an SNR of…
|-
| 85 – 90
| ≤20
|-
| 90 – 95
| 20 – 30
|-
| 95 – 100
| 25 – 35
|-
| 100 – 105
| ≥30
|}

{|
|width="100%"|
1 Based on instantaneous noise levels, not the daily personal noise exposure.

– Higher levels of protection can be achieved through dual protection, i.e. wearing ear-muffs over ear-plugs.
|}

There are several other factors that influence the choice of which type of hearing protector an employee may wish to use, as outlined in Part 5 of the NAW Regulations, which also state that “wherever possible the employer should make more than one type of protector available (making sure that each is suitable for the noise and jobs to be done) to allow the user a personal choice”.

Employees are often reluctant to use hearing protection, are forgetful, or do not apply protection correctly. A programme of monitoring, supervision, warning notices, instruction, and training is needed to ensure they are used. It is also important that a system of maintenance is employed, to ensure that the hearing protection maintains its level of noise reduction and does not become defective over time.

=== Hearing Protection Zones (HPZ) ===

Regulation 7 of the NAW Regulations indicates If any area in the workplace is likely to be exposed to noise levels at or above the upper exposure action value (UEAV) then the employer must ensure that:

• the area is designated a Hearing Protection Zone (HPZ); 
• the area is demarcated and identified by means of the sign specified for the purpose of indicating that ear protection must be worn; 
• access to the area is restricted where this is practicable and the risk from exposure justifies it; and 
• no employee enters that area unless that employee is wearing personal hearing protectors, so far as is reasonably practicable.

The boundaries of HPZs should be considered carefully, i.e. they should avoid overlapping commonly used walkways and should not extend further than is necessary to protect people carrying out their normal work. In situations where the boundaries of a zone cannot be marked, then attaching hearing protection zone signs to specific tools is an appropriate alternative.

=== Information, Instruction, and Training ===

Regulation 10 of the NAW Regulations indicates that the employer must provide ‘information, instruction, and training’ to employees who are exposed to above the LEAV. It is important for the employer to tell employees:

• their likely level of noise exposure and the health risk this carries; 
• what the employer is doing to control risks and exposure to noise; 
• when and how the employee can obtain hearing protection and when they should use it; 
• how the employee should be using hearing protection and noise control equipment in the correct way to minimize their risk, and how they can identify and report defects; 
• what the employees’ duties are under the NAW Regulations; and 
• how the employer is providing a health surveillance system; and 
• what symptoms of hearing damage the employee should look out for, and to whom and how they should report this.

This information, instruction, and training can be provided in any way, providing the employee can find it easy to understand. The HSE’s ‘Noise: Don’t lose your hearing!’ pocked card can be handed out to supplement this.

It is also a requirement to discuss the risk assessment and all plans relating to controlling noise exposure with a trade union-appointed safety representative, or for groups of workers not covered by this, an elected employee representative.

=== Health Surveillance ===

Regulation 9 of the NAW Regulations state that there is significant evidence which links the regular exposure to noise levels above the exposure action values to long term health risks and hearing damage. Therefore, the employer should provide health surveillance to:

• all employees who are regularly exposed to noise levels above the upper exposure action values (UEAV); or 
• employees who are occasionally exposed above the UEAV, or who are exposed between the lower (LEAV) and upper (UEAV) thresholds but who are known to be particularly sensitive to noise, i.e. from medical history, audiometric testing or a history of noise exposure at previous jobs, or a family history of early-onset deafness.

Health surveillance is a programme of health checks which usually involves regular hearing checks (audiometric testing), keeping health records, and referring employees to a doctor if/when hearing damage is identified. It is useful in waring employees if they exhibit early signs of hearing damage to give the opportunity to do something to prevent the damage from getting worse. It is also effective for the employer to identify whether noise control measures are working.

Surveillance can be introduced at any time for existing employees and should be introduced straightaway for new employees, to allow a baseline to be taken. Annual checks for the first two years (followed by three-yearly checks after this unless a problem is detected or the risk of hearing damage is high) should be conducted by someone with appropriate training, with the whole surveillance programme under the control of an occupational health professional.

== Ongoing Assessments ==

Regulation 5 of the NAW Regulations indicate that the employer should implement an ongoing control programme in managing noise exposure risks. It may be necessary to review and produce an updated risk assessment when circumstances change, for example, if:

• circumstances change in the workplace, i.e. new equipment is installed, older machinery ceases to be used, shift patterns are changed, any reason that employees’ level of noise exposure may have changed; 
• noise control measures have been implemented since the previous assessment and the impact on employees’ exposure needs to be re-assessed; 
• the employer becomes aware of improved working methods and noise-control techniques that are new to the industry and could be applied to the workplace; 
• control measures that could not be implemented at the time of the original assessment become more viable to do so, i.e. because of new technology or reduced costs; and/or 
• continued health surveillance shows that employees’ hearing is being damaged, suggesting that noise control methods are not being properly implemented or are not effective enough.

The NAW Regulations indicate that even if none of the points above are true, the assessment should still be reviewed at least every two years.

Article reproduced from [https://www.parkerjonesacoustics.com/insights/noise-at-work-assessments-explained Noise at Work Assessments Explained] by [https://www.parkerjonesacoustics.com ParkerJones Acoustics]

Noise at Work Assessment

2020-02-10T17:28:12Z

ParkerJonesAcoustics: Created page with "= The Control of Noise at Work Regulations = The ‘Control of Noise at Work Regulations 2005’ (‘the NAW Regulations’) sets out the legal requirements in respect of protec..."

= The Control of Noise at Work Regulations =

The ‘Control of Noise at Work Regulations 2005’ (‘the NAW Regulations’) sets out the legal requirements in respect of protecting employees against risks to their health and safety arising from exposure to noise whilst at work. The aim of the NAW Regulations is to protect workers from suffering long term hearing damage and tinnitus as a result of prolonged exposure to high noise levels in the workplace.

== What must an employer do? ==

The NAW Regulations apply to all workplaces and mean that employers are legally obliged to risk assess the exposure of their employees’ exposure to noise within the working environment. The employer must employ appropriate control measures to reduce noise exposure where necessary.

Regulation 5 of the NAW Regulations states that a detailed Noise at Work Risk Assessment (the purpose of this document) must be undertaken if an employee is likely to be exposed to noise at or above lower exposure action values. This may occur if a workplace is considered to be noisier than everyday life.

== Noise Exposure Action Values/Limits ==

In accordance with Regulation 4 of the NAW Regulations, a set of noise exposure action values are set which relate to the average levels of noise exposure over a working day or week, and the peak sound pressure exposure to which employees are exposed to in a working day. In summary:

• ‘exposure action values’ are the levels of exposure to noise at which employees can be exposed to, but employers are required to take certain actions to mitigate this risk, including the provision of hearing protection; and 
• ‘exposure limit values’ are the levels of noise exposure at which an employee must not be exposed to, after taking into account the noise reduction provided by personal hearing protection.

As per Regulation 4, the following exposure action and limit values are defined:

Table 1 – Definition of the exposure action and limit values

Action Level

Threshold Values

Actions Required if Thresholds Exceeded

Lower Exposure Action Value(LEAV)

· a daily personal exposure level (LEP,d)1 of 80 dB(A).

· a peak sound pressure level (LCPeak) of 135 dB(C).

(these limits do not account for hearing protection)

In the first instance, the employer should explore other methods of reducing noise levels to as low a level as is reasonably practicable. If the LEAV is still exceeded, then hearing protection is recommended and the employer must provide personal hearing protectors upon the request of any employee in this exposure category (though it must not be compulsory for the employee to wear them unless they are in a designated Hearing Protection Zone (HPZ).

The employer must also provide ‘information, instruction, and training’ to employees who are exposed to above the LEAV.

Upper Exposure Action Value(UEAV)

· a daily personal exposure level (LEP,d)1 of 85 dB(A).

· a peak sound pressure level (LCPeak) of 137 dB(C).

(these limits do not account for hearing protection)

The employer shall reduce exposure to as low a level as is reasonably practicable by establishing and implementing a programme of organisational and technical measures, excluding the provision of personal hearing protectors, which is appropriate to the activity (see following subsections).If the UEAV is still exceeded, then hearing protection is compulsory to employees in this exposure category and must be supplied by the employer. If a particular area is above the UEAV, then this area must be designated as a HPZ. The employers must ensure that affected employees or employees entering the HPZ use hearing protection, who also have a duty to protect themselves.

Exposure Limit Value (ELV)

· a daily personal exposure level (LEP,d)1 of 87 dB(A).

· a peak sound pressure level (LCPeak) of 140 dB(C).

(the effect of personal hearing protection is accounted for in these limits)

Employees must not be permitted to be exposed above the exposure limits (after accounting for the noise reduction provided by personal hearing protection).

Action must be taken immediately to reduce exposure if this limit has been exceeded. The employer must review the programme of control measures, considering the technical and organisational controls, the adequacy of any hearing protection supplied and systems in place that ensures noise-control measures and hearing protection are properly used and maintained.

1 These limits can also apply to a weekly personal exposure level (LEP,w)

2 It may be necessary to conduct ongoing health surveillance for the exceedance of the LEAV and UEAV.

== What do these action values mean? How do I mitigate noise? ==

In summary, if the noise exposure action values are exceeded then the employer may be required to

* reduce the noise exposure that produces these risks to as low a level as is reasonably practicable by either
** reducing noise at source, i.e. by using quieter equipment, a different process, engineering controls, etc.;
** reducing noise levels in the facility, i.e. through sound absorption, keeping noisy machinery away from quieter areas, screens, barriers, or enclosures; and/or
** implementing organisational measures which reduce the length of time that employees are exposed to noise, i.e. turning off equipment when not in use, introducing job rotation so employees are doing a mixture of noise and quiet tasks rather than spending all day working with high noise level equipment;
* provide employees with hearing protection if the noise exposure cannot be reduced enough by the aforementioned measures and the noise levels remain above the exposure action values;
* provide employees with information, instruction, and training on noise in the workplace; and
* carry out health surveillance where there is a risk because of exposure to loud noise.

Paragraph 66 of Regulation 6 of the NAW Regulations indicates that the employer should generally be seeking to reduce the risk of noise exposure irrespective of whether any exposure action values are exceeded. It may also be necessary to carry out ongoing reviews to the risk assessment at set periods, or when circumstances change.

=== Organisational and Technical Measures of Noise Reduction ===

Regulation 6 of the NAW Regulations indicates that “the employer shall ensure that risk from the exposure of his employees to noise is either eliminated at source or, where this is not reasonably practicable, reduced to as low a level as is reasonably practicable….. If any employee is likely to be exposed to noise at or above an upper exposure action value, the employer shall reduce exposure to as low a level as is reasonably practicable by establishing and implementing a programme of organisational and technical measures, excluding the provision of personal hearing protectors, which is appropriate to the activity.” The table below provides examples of such measures.

Table 2: Methods of controlling noise through organisational and technical measures

{|
|width="50%"| Action
|width="50%"| Example Measures
|-
| Reduce noise levels at source
|
* Sourcing quieter alternative equipment.
* Using a different quieter working process that achieves the same production outcome.
* Implement a maintenance programme to ensure that noise levels are not significantly raised from poorly maintained and old equipment.
* Apply noise silencing or vibration dampening parts to existing equipment.
* Using anti-vibration mounts to isolate the equipment from the structure to reduce structure-borne noise throughout a building.
* Attaching silencers to noisy air or gas stream inlets and exhausts.
* Fitting a noise enclosure around the machine (or the noisy part of a machine).
* Using active noise control systems around equipment that are particularly noisy at low frequency.
|-
| Reduce noise propagation throughout the workplace
|
* Placing noise equipment in an area with fewer employees and therefore limiting exposure to workers who are not directly operating this equipment.
* Increasing the distance between the source of noise and the operator/other works, which could be achieved by a remote control panel in some cases.
* Directing the noisiest parts of the equipment (i.e. the exhaust of a compressed air system) away from the working area.
* Using screens and barriers between the sound source and people, to reduce direct sound.
* Providing a ‘noise haven’ for employees, including operators, where controlling noise levels at source would be difficult.
* Providing rest facilities where the level of noise exposure is low.
* Reducing the ‘reverberation time’ in the building by adding acoustically absorbent material, either retrofitting acoustic panelling/suspended baffles or by using absorbent surface finishes (such as ceiling tiles and perforated metal roof liners).
|-
| Organisational controls
|
* Only operating equipment when strictly necessary and not leaving noisy equipment to idle.
* Reducing the number of employees working in noisy areas.
* Introducing job rotation so employees are doing a mixture of noise and quiet tasks rather than spending all day working with high noise level equipment.
* Training employees on how to reduce their risk to noise exposure, and potentially developing in-house skills noise control, to ensure that workers are able to identify when equipment is producing louder than usual noise levels and how they might be able to reduce this.
* Generally limiting the duration and intensity of exposure to noise, and having appropriate work schedules with adequate rest periods.
|}

=== Personal Hearing Protection ===

After the measures with Regulation 6 (summarised in the previous subsection) have been explored, the next step is to consider providing personal hearing protection.

Regulation 7 of the NAW Regulations indicate that hearing protection is compulsory for employees exposed to levels above the upper exposure action value (UEAV), though this is not compulsory during the quieter times of the day or if the employee is in a quiet area. It is also compulsory for any employee entering a Hearing Protection Zone (HPZ).

Hearing protection is not compulsory for employees exposed to levels below the UEAV. It is not beneficial to enforce employees to wear hearing protection when not necessary, as this can lead to isolation, decreased communication, uncomfortable working conditions and a decreased ability to hear alarms and sirens.

It is also not strictly beneficial to use hearing protectors which overprotect, for the reasons above. The main aim of hearing protection is to reduce noise levels at the ear to below at least the UEAV (85 dB(A)), but they should be avoided if they reduce noise levels to below 70 dB(A).

The table below shows the ‘single number rating’ (SNR) protection factor that is likely to be suitable for different levels of noise. The SNR value is typically stated with the hearing protection device. This is based upon the information in the NAW Regulations, and in BS EN 458:2004: Hearing protectors.

Table 3: Required protection factors for hearing protection

A-Weighted Noise Level (dB(A)) 1

Select a protector with an SNR of…

85 – 90

≤20

90 – 95

20 – 30

95 – 100

25 – 35

100 – 105

≥30

1 Based on instantaneous noise levels, not the daily personal noise exposure.

– Higher levels of protection can be achieved through dual protection, i.e. wearing ear-muffs over ear-plugs.

There are several other factors that influence the choice of which type of hearing protector an employee may wish to use, as outlined in Part 5 of the NAW Regulations, which also state that “wherever possible the employer should make more than one type of protector available (making sure that each is suitable for the noise and jobs to be done) to allow the user a personal choice”.

Employees are often reluctant to use hearing protection, are forgetful, or do not apply protection correctly. A programme of monitoring, supervision, warning notices, instruction, and training is needed to ensure they are used. It is also important that a system of maintenance is employed, to ensure that the hearing protection maintains its level of noise reduction and does not become defective over time.

=== Hearing Protection Zones (HPZ) ===

Regulation 7 of the NAW Regulations indicates If any area in the workplace is likely to be exposed to noise levels at or above the upper exposure action value (UEAV) then the employer must ensure that:

• the area is designated a Hearing Protection Zone (HPZ); 
• the area is demarcated and identified by means of the sign specified for the purpose of indicating that ear protection must be worn; 
• access to the area is restricted where this is practicable and the risk from exposure justifies it; and 
• no employee enters that area unless that employee is wearing personal hearing protectors, so far as is reasonably practicable.

The boundaries of HPZs should be considered carefully, i.e. they should avoid overlapping commonly used walkways and should not extend further than is necessary to protect people carrying out their normal work. In situations where the boundaries of a zone cannot be marked, then attaching hearing protection zone signs to specific tools is an appropriate alternative.

=== Information, Instruction, and Training ===

Regulation 10 of the NAW Regulations indicates that the employer must provide ‘information, instruction, and training’ to employees who are exposed to above the LEAV. It is important for the employer to tell employees:

• their likely level of noise exposure and the health risk this carries; 
• what the employer is doing to control risks and exposure to noise; 
• when and how the employee can obtain hearing protection and when they should use it; 
• how the employee should be using hearing protection and noise control equipment in the correct way to minimize their risk, and how they can identify and report defects; 
• what the employees’ duties are under the NAW Regulations; and 
• how the employer is providing a health surveillance system; and 
• what symptoms of hearing damage the employee should look out for, and to whom and how they should report this.

This information, instruction, and training can be provided in any way, providing the employee can find it easy to understand. The HSE’s ‘Noise: Don’t lose your hearing!’ pocked card can be handed out to supplement this.

It is also a requirement to discuss the risk assessment and all plans relating to controlling noise exposure with a trade union-appointed safety representative, or for groups of workers not covered by this, an elected employee representative.

=== Health Surveillance ===

Regulation 9 of the NAW Regulations state that there is significant evidence which links the regular exposure to noise levels above the exposure action values to long term health risks and hearing damage. Therefore, the employer should provide health surveillance to:

• all employees who are regularly exposed to noise levels above the upper exposure action values (UEAV); or 
• employees who are occasionally exposed above the UEAV, or who are exposed between the lower (LEAV) and upper (UEAV) thresholds but who are known to be particularly sensitive to noise, i.e. from medical history, audiometric testing or a history of noise exposure at previous jobs, or a family history of early-onset deafness.

Health surveillance is a programme of health checks which usually involves regular hearing checks (audiometric testing), keeping health records, and referring employees to a doctor if/when hearing damage is identified. It is useful in waring employees if they exhibit early signs of hearing damage to give the opportunity to do something to prevent the damage from getting worse. It is also effective for the employer to identify whether noise control measures are working.

Surveillance can be introduced at any time for existing employees and should be introduced straightaway for new employees, to allow a baseline to be taken. Annual checks for the first two years (followed by three-yearly checks after this unless a problem is detected or the risk of hearing damage is high) should be conducted by someone with appropriate training, with the whole surveillance programme under the control of an occupational health professional.

== Ongoing Assessments ==

Regulation 5 of the NAW Regulations indicate that the employer should implement an ongoing control programme in managing noise exposure risks. It may be necessary to review and produce an updated risk assessment when circumstances change, for example, if:

• circumstances change in the workplace, i.e. new equipment is installed, older machinery ceases to be used, shift patterns are changed, any reason that employees’ level of noise exposure may have changed; 
• noise control measures have been implemented since the previous assessment and the impact on employees’ exposure needs to be re-assessed; 
• the employer becomes aware of improved working methods and noise-control techniques that are new to the industry and could be applied to the workplace; 
• control measures that could not be implemented at the time of the original assessment become more viable to do so, i.e. because of new technology or reduced costs; and/or 
• continued health surveillance shows that employees’ hearing is being damaged, suggesting that noise control methods are not being properly implemented or are not effective enough.

The NAW Regulations indicate that even if none of the points above are true, the assessment should still be reviewed at least every two years.

Article reproduced from [https://www.parkerjonesacoustics.com/insights/noise-at-work-assessments-explained Noise at Work Assessments Explained] by [https://www.parkerjonesacoustics.com ParkerJones Acoustics]

Sound insulation in buildings

2020-01-18T20:58:59Z

ParkerJonesAcoustics:

= Introduction =

Sound insulation describes the reduction in sound across a partition. The sound insulation across a good conventional, lightweight, office to office construction is typically in the order of 45 dB Dw.

This means that if the sound level in the source room is around 65 dB (a typical level for speech), the sound level in the adjacent room, the receiver room, will be approximately 20 dB (barely audible).

If sound levels are increased in the source room to 75 dB (raised voice), sound levels within the adjacent room will also increase to around 30 dB (audible). Sound insulation therefore describes the level of sound lost across a partition and not the level of sound within a adjacent room.

= Privacy =

Privacy describes the perceived sound reduction across a wall. Privacy is a function of both sound insulation and background noise. Background noise is made up of services noise and environmental noise sources breaking in through the facade or open windows, vents etc.

If the background noise within a room is increased by 5 to 10 dB, the perceived level of privacy across a partition is also increased by 5 to 10 dB. Therefore, when looking at required sound insulation levels on-site, it is important to consider both the background noise in the receiver room and the sound insulation across the partition.

= Subjective description of sound insulation =

The table below provides an illustrative representation of privacy. This table specifies two Dw levels for a partition, one for background noise levels in the receiver room of 35 dBA1, and the second for background noise levels of 40 dBA2.

[[File:Illustrative_representation_of_privacy.jpg|link=File:Illustrative_representation_of_privacy.jpg]]

= Rw (Lab Tested Sound Reduction Index) and Dw (On Site Sound Reduction Index) =

Two parameters are used to describe the sound insulation of a partition, Dw and Rw. Dw represents the sound insulation between rooms on-site. Since these figures describe the final site requirements, Dw levels are specified by clients and Building Regulations. Rw represents the lab tested sound insulation of an element making up a partition wall/floor type. Due to flanking and other factors, lab rated sound reduction levels will not be achieved on-site.

Conventionally, there is a 5 - 10 dB reduction between a Rw lab tested figure and an on-site Dw figure. The conversion between Dw and Rw is relatively complex and takes into consideration receiver room volume, receiver room reverberation times and the area of the separating partition. The conversion between Rw and Dw should always be calculated.

[[File:Rw vs Dntw.jpg]]

NB: Approved document E, Resistance to the passage of sound, defines the sound reduction index (which it describes as 'R') as a '...quantity, measured in a laboratory, which characterises the sound insulating properties of a material or building element in a stated frequency band. See BS EN ISO 140-3:1995.'

-----
This article was created by --[[User:MACH_Acoustics|MACH Acoustics]] 13:06, 28 November 2013 (UTC)

= Related articles on Designing Buildings Wiki =

* Acoustic insulation market.
* Acoustic design for health and wellbeing.
* Acoustic louvre.
* Airborne sound.
* Approved Document E.
* Ash deafening.
* BREEAM Insulation.
* Building acoustics.
* Building Bulletin 93: acoustic design of schools.
* Decibel.
* Flanking sound.
* Impact sound.
* Mineral wool.
* Noise - doors and windows.
* Noise nuisance.
* Part E compliance.
* Pre-completion sound testing.
* Reverberation.
* Robust details certification scheme.
* [[Rw_and_Dw/DnTw_in_Acoustics_-_What_do_they_mean?|Rw and Dw/DnTw in Acoustics]]
* Sound absorption.
* Sound absorption coefficient.
* Sound frequency.
* Sound insulation in dwellings: Part 1: An introduction (GG 83-1).
* Sound insulation in dwellings: Part 3: Material change of use (conversions) (GG 83-3).
* Sound insulation testing.
* Sound v noise.
* Sound reduction index (SRI).
* Structure-borne sound.

= External references =

* MACH Acoustics: Subjective Evaluation and Conversion between RW and DW.
* ParkerJones Acoustics: [https://www.parkerjonesacoustics.com/insights/articles/rw-and-dntw Rw and DnT,w – What do they mean?]

[[Category:Theory]] [[Category:Standards_/_measurements]]

User:ParkerJonesAcoustics

2020-01-13T14:17:46Z

ParkerJonesAcoustics:

[https://www.parkerjonesacoustics.com Acoustics, Noise and Vibration Consultant] based in Bristol and the South West, working around the UK, including Birmingham, London, Manchester, Cardiff, and Edinburgh.

We work across [https://www.parkerjonesacoustics.com/sectors all areas of acoustics] in the built environment, [https://www.parkerjonesacoustics.com/services/industrial-noise-assessments industry], infrastructure, power and mining/minerals.

Need a [https://www.parkerjonesacoustics.com/services/noise-surveys noise survey], a [https://www.parkerjonesacoustics.com/services/sound-testing sound test], vibration monitoring or any aspect or [https://www.parkerjonesacoustics.com/services/building-acoustics acoustics/noise/vibration design] from feasibility, through planning, through detailed design, construction and completion, [https://www.parkerjonesacoustics.com/contact-us then give us a call.]

Our biggest specialism in the detailed [https://www.parkerjonesacoustics.com/services/building-acoustics acoustic design of residential, educational and healthcare buildings].

Talk to one of our [https://www.parkerjonesacoustics.com acoustic consultants] today.

chris@parkerjonesacoustics.com

01179146558

Sound insulation testing

2020-01-13T02:13:45Z

ParkerJonesAcoustics:

== Sound Testing to comply with Part E for Residential Developments ==

There are many sets of Building Regulations requirements which a new or refurbished residential development must meet. One of these, is to achieve a minimum standard of sound insulation performance internally between dwellings. This is an important regulation, as we seek some level of sound privacy from our neighbours, ensuring we can live and sleep in peace.

=== What are the Sound Insulation targets I need to achieve? ===

The specific acoustic performance requirements for new builds and conversions are set within [http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf Approved Document E ‘resistance to the passage of sound’], as shown in the table.

Requirement E1 – on-site airborne sound insulation performance targets for separating (party) walls and floors

[[File:Sound insulation targets for residential.jpg]]

[http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf Approved Document E] classes ‘rooms for residential purposes’ means a room, or a suite of rooms, which is not a dwelling-house or a flat and which is used by one or more persons to live and sleep and includes a room in a hostel, a hotel, a boarding house, a hall of residence or a residential home, but does not include a room in a hospital or other similar establishment used for patient accommodation.

As shown above, the criteria for refurbishments are slightly more lenient than for new builds. This recognises that it can be more difficult to soundproof an existing structure if it cannot replaced, compared to implementing a construction from scratch.

This relates to sound insulation internally, between residential properties which share a separating wall or floor. It relates to separate properties, not internal walls/floors within a dwelling, which carry a much lower requirement for sound insulation which is not subject to sound testings.

Standards for noise ingress from outside (i.e. road traffic) are not covered under ADE and the Building Regulations, with the local planning authority having more of an input into what they consider to be a suitable internal noise level target.

=== What is Airborne Sound Insulation and a DnT,w + Ctr? ===

Airborne sound insulation relates to sound that travels via the air and through separating structures between rooms. For example, airborne sound across a lightweight floor would pass through the plasterboard ceiling, into the floor void, through the floorboards and into the room. It relates to noise sources such as speech, music, television sound…any noise source that radiates into the air, rather than directly into the structure.

The DnT,w + Ctr relates to a level of on-site sound insulation. In simple terms, put a noise source in one room (the ‘source room’), measure the noise level, then go next door (the ‘receiver room’) and measure again, then calculate the difference. Well actually, this would be a ‘D’. A Dw is similar, but with the ‘w’ denoting a weighting across frequency which accounts for the way humans perceive different frequencies. A DnT,w is a Dw which is then ‘normalised’ to account for the reverberation time of the room (the ‘nT’), recognising that the level difference is dependant on how reverberant the receiver room is, and that every room will have a slightly different reverberation time, hence we need to normalise the result to assess every sound test on a level playing field against a fixed target. A DnT,w + Ctr then adds the addition of a low frequency correction (the ‘Ctr’), as low frequency noise is difficult to control and therefore the regulations add this correction to improve the standard of sound insulation against low frequency noise such as music.

Confused? Lets look at it really roughly. Take a source level in one flat of 100 dB(A), then a receiver level in the neighbouring flat of 55 dB(A), the level difference is 45 dB, hence our sound insulation performance should be somewhere in the region of 45 dB DnT,w + Ctr…

The higher the DnT,w + Ctr, the better the level of airborne sound insulation.

=== What is Impact Sound Insulation and an L’nT,w? ===

Impact sound insulation relates to noise generated by actual impact on a structure. Hence this typically is only assessed for intermediate floors, to consider noise such as footsteps, chair scrapes and any other object being dropped or impacting on the floor.

The L’nT,w is determined from measuring sound levels within a room where the floor above is being excited by an impact. Your acoustic consultant will use what’s called a ‘tapping machine’ to do this, which drops a series of weights/hammers on the floor in regular succession at a fixed force (as if the acoustic engineer varied the force every time they test, they’d get completely different results!).

The lower the L’nT,w, the better the level of impact sound insulation.

=== What does Sound Testing actually involve? ===

For compliance with the Building Regulations, the acoustic testing must be conducted by a qualified acoustic engineer who is accredited to conduct sound testing by an organisation such as [https://www.ukas.com/news/technical-bulletin-sound-insulation-testing-and-reuse-of-reverberation-time-measurements/ Ukas] or the [https://www.association-of-noise-consultants.co.uk/services/sound-insulation-testing/ Association of Noise Consultants]. Such an engineer will be using expensive equipment including a Class 1 sound level meter which costs several thousand pounds… so don’t try this with your noise meter bought for a few quid!

Airborne sound insulation tests are conducted by placing a loudspeaker, or two loudspeakers in the ‘source’ room. These loudspeakers are use to play white or pink noise at a very high amplitude, to the tune of 95 – 110 dB(A) within the room (the acoustic engineer will be wearing hearing protection!). The reason for using this type of noise, is that it is constant in amplitude, with an even spread of sound energy across frequency, keeping our test nice and consistent. The engineer will use their sound level meter to make a series of measurements in the source room. They will then go to the adjacent room (with the loudspeaker still on) and take a series of measurements within the ‘receiver’ room.

After turning off the loudspeaker, two other tests will be made in the receiver room. One is to measure the reverberation time (to get the ‘nT’ correction in DnT,w + Ctr), which can be achieved by generating an impulse in the room, using the sound level meter to measure/calculate the time taken for sound to decay by 60 dB. The impulse can be made by popping a balloon, shooting a starter pistol, or using the loudspeaker to generate white noise and then abruptly turning it off. The reverberation time affects how much sound energy bounces around the room, therefore affecting sound levels in the receiver room, which therefore affects the level difference from the sound source next door. The second test, is to measure background noise. If we’re measuring a high level of sound insulation then we might expect that background noise from other noise sources will be at a similar level to the level in the receiver room from our noise source next door, therefore we have to make a correction for this.

Putting these all together, the measurements of level difference, reverberation time, and background noise, enables us to calculate the result DnT,w + Ctr.

Impact sound insulation tests as alluded to earlier, are conducted using a ‘tapping’ machine. This machine is placed upon the floor and set to work, where the acoustic consultant will then move downstairs to measure in the room below. As per airborne sound tests, the acoustic engineer will measure reverberation time and background noise in the receiver room. Putting all this together enables the consultant to calculate the L’nT,w.

=== How many Sound Tests do I need? ===

In large scale residential developments, we’re going to have a certain level of repeatability. Do we need to test every single wall and floor? No. Lets say for example, we have a building containing 10 very similar flats, with the same constructions and construction detailing between them. For this, ADE indicates that we would only need 1 ‘set’ of tests, as it suggests that at least ‘one set of tests for every ten dwelling-houses, flats or rooms for residential purposes in a group or sub-group’.

So what defines a ‘set’ of tests?

{|
|width="100%"| Sets of tests in flats with a separating floor and a separating wall
|-
| [[File:Sound Test sets 1 no text.png]]
|-
|
One set of tests should compromise 6 tests (4 airborne, 2 impact):

• 1 airborne test across a wall between (where possible) a pair of living rooms

• 1 airborne test across a wall between (where possible) a pair of bedrooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of living rooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of bedrooms
|}

{|
|width="50%"| [[File:Sound Test sets 2 no text.png]]
|width="50%"|
Sets of tests in flats with separating floors but without separating walls

One set of tests should compromise 4 tests (2 airborne, 2 impact):

• 1 airborne and 1 impact test across a floor between (where possible) a pair of living rooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of bedrooms
|}

{|
|width="100%"| Sets of tests in dwelling-houses with separating walls but no separating floors
|-
| [[File:Sound Test sets 3 no text.png]]
|-
|
One set of tests should compromise 2 tests (2 airborne):

• 1 airborne test across a wall between (where possible) a pair of living rooms

• 1 airborne test across a wall between (where possible) a pair of bedrooms
|}

=== What condition should my site be in for Sound Testing? ===

Sound testing should ideally be conducted after completion of the building works, or as close to completion as possible. A failed acoustic test can often be down to constructions not being completed, penetrations and air gaps not being sealed, doors not being in place…

Your acoustic consultant will also ask for a bit of quiet. If you ask your acoustic engineer to come to site a few weeks before completion and there are still a lot of construction works and snagging going on, then the acoustic testing results may be adversely influenced by this noise.

Your acoustic consultant may thank you if you can provide 240v power on site. Whilst some acoustic engineers use battery-operated equipment, many don’t, and having to carry a transformer with an extension lead can mean that testing takes longer, which may mean more site visits, and therefore more cost for you.

Lastly, something that is often overlooked, is that impact sound insulation testing should be conducted in residential developments without the floor finish. A carpet floor finish is a very good dampener of impacts upon the floor. But in a few years, what if the occupant decides they would like to change this to hard flooring? Answer, the level of impact sound insulation could get much worse. Therefore to safeguard against this, impact sound insulation testing must be conducted without the floor finish (unless it can be argued that the finish is integral and cannot be changed later down the line). It’s for this reason that party floors usually have an acoustic/resilient underlay within the floor construction, or beneath the floor finish.

[https://www.parkerjonesacoustics.com/insights/articles/sound-testing-explained Article was written and originally produced by ParkerJones Acoustics.]

File:Sound Test sets 3 no text.png

2020-01-13T02:13:02Z

ParkerJonesAcoustics: Sound tests - number of tests in a set

Sound tests - number of tests in a set

File:Sound Test sets 2 no text.png

2020-01-13T02:12:28Z

ParkerJonesAcoustics: Sound tests - number of tests in a set

Sound tests - number of tests in a set

File:Sound Test sets 1 no text.png

2020-01-13T02:12:00Z

ParkerJonesAcoustics: Sound tests - number of tests in a set

Sound tests - number of tests in a set

File:Sound insulation targets for residential.jpg

2020-01-13T02:10:29Z

ParkerJonesAcoustics: Approved Document E targets for sound insulation between residential dwellings

Approved Document E targets for sound insulation between residential dwellings

Sound insulation testing

2020-01-13T02:07:09Z

ParkerJonesAcoustics: Created page with "== Sound Testing to comply with Part E for Residential Developments == There are many sets of Building Regulations requirements which a new or refurbished residential developmen..."

== Sound Testing to comply with Part E for Residential Developments ==

There are many sets of Building Regulations requirements which a new or refurbished residential development must meet. One of these, is to achieve a minimum standard of sound insulation performance internally between dwellings. This is an important regulation, as we seek some level of sound privacy from our neighbours, ensuring we can live and sleep in peace.

=== What are the Sound Insulation targets I need to achieve? ===

The specific acoustic performance requirements for new builds and conversions are set within [http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf Approved Document E ‘resistance to the passage of sound’], as shown in the table.

Requirement E1 – on-site airborne sound insulation performance targets for separating (party) walls and floors

Separating Element

Airborne sound insulation

DnT,w + Ctr dB

(minimum values)

Impact sound insulation

L’nT,w dB

(maximum values)

Purpose built dwelling-houses and flats (new build)

Walls

45

–

Floors and Stairs

45

62

Dwelling-houses and flats formed by material change of use (refurbishment)

Walls

43

–

Floors and Stairs

43

64

Purpose built rooms for residential purposes (new build)

Walls

43

–

Floors and Stairs

43

62

Rooms for residential purposes formed by material change of use (refurbishment)

Walls

43

–

Floors and Stairs

43

62

[http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADE_2003.pdf Approved Document E] classes ‘rooms for residential purposes’ means a room, or a suite of rooms, which is not a dwelling-house or a flat and which is used by one or more persons to live and sleep and includes a room in a hostel, a hotel, a boarding house, a hall of residence or a residential home, but does not include a room in a hospital or other similar establishment used for patient accommodation.

As shown above, the criteria for refurbishments are slightly more lenient than for new builds. This recognises that it can be more difficult to soundproof an existing structure if it cannot replaced, compared to implementing a construction from scratch.

This relates to sound insulation internally, between residential properties which share a separating wall or floor. It relates to separate properties, not internal walls/floors within a dwelling, which carry a much lower requirement for sound insulation which is not subject to sound testings.

Standards for noise ingress from outside (i.e. road traffic) are not covered under ADE and the Building Regulations, with the local planning authority having more of an input into what they consider to be a suitable internal noise level target.

=== What is Airborne Sound Insulation and a DnT,w + Ctr? ===

Airborne sound insulation relates to sound that travels via the air and through separating structures between rooms. For example, airborne sound across a lightweight floor would pass through the plasterboard ceiling, into the floor void, through the floorboards and into the room. It relates to noise sources such as speech, music, television sound…any noise source that radiates into the air, rather than directly into the structure.

The DnT,w + Ctr relates to a level of on-site sound insulation. In simple terms, put a noise source in one room (the ‘source room’), measure the noise level, then go next door (the ‘receiver room’) and measure again, then calculate the difference. Well actually, this would be a ‘D’. A Dw is similar, but with the ‘w’ denoting a weighting across frequency which accounts for the way humans perceive different frequencies. A DnT,w is a Dw which is then ‘normalised’ to account for the reverberation time of the room (the ‘nT’), recognising that the level difference is dependant on how reverberant the receiver room is, and that every room will have a slightly different reverberation time, hence we need to normalise the result to assess every sound test on a level playing field against a fixed target. A DnT,w + Ctr then adds the addition of a low frequency correction (the ‘Ctr’), as low frequency noise is difficult to control and therefore the regulations add this correction to improve the standard of sound insulation against low frequency noise such as music.

Confused? Lets look at it really roughly. Take a source level in one flat of 100 dB(A), then a receiver level in the neighbouring flat of 55 dB(A), the level difference is 45 dB, hence our sound insulation performance should be somewhere in the region of 45 dB DnT,w + Ctr…

The higher the DnT,w + Ctr, the better the level of airborne sound insulation.

=== What is Impact Sound Insulation and an L’nT,w? ===

Impact sound insulation relates to noise generated by actual impact on a structure. Hence this typically is only assessed for intermediate floors, to consider noise such as footsteps, chair scrapes and any other object being dropped or impacting on the floor.

The L’nT,w is determined from measuring sound levels within a room where the floor above is being excited by an impact. Your acoustic consultant will use what’s called a ‘tapping machine’ to do this, which drops a series of weights/hammers on the floor in regular succession at a fixed force (as if the acoustic engineer varied the force every time they test, they’d get completely different results!).

The lower the L’nT,w, the better the level of impact sound insulation.

=== What does Sound Testing actually involve? ===

For compliance with the Building Regulations, the acoustic testing must be conducted by a qualified acoustic engineer who is accredited to conduct sound testing by an organisation such as [https://www.ukas.com/news/technical-bulletin-sound-insulation-testing-and-reuse-of-reverberation-time-measurements/ Ukas] or the [https://www.association-of-noise-consultants.co.uk/services/sound-insulation-testing/ Association of Noise Consultants]. Such an engineer will be using expensive equipment including a Class 1 sound level meter which costs several thousand pounds… so don’t try this with your noise meter bought for a few quid!

Airborne sound insulation tests are conducted by placing a loudspeaker, or two loudspeakers in the ‘source’ room. These loudspeakers are use to play white or pink noise at a very high amplitude, to the tune of 95 – 110 dB(A) within the room (the acoustic engineer will be wearing hearing protection!). The reason for using this type of noise, is that it is constant in amplitude, with an even spread of sound energy across frequency, keeping our test nice and consistent. The engineer will use their sound level meter to make a series of measurements in the source room. They will then go to the adjacent room (with the loudspeaker still on) and take a series of measurements within the ‘receiver’ room.

After turning off the loudspeaker, two other tests will be made in the receiver room. One is to measure the reverberation time (to get the ‘nT’ correction in DnT,w + Ctr), which can be achieved by generating an impulse in the room, using the sound level meter to measure/calculate the time taken for sound to decay by 60 dB. The impulse can be made by popping a balloon, shooting a starter pistol, or using the loudspeaker to generate white noise and then abruptly turning it off. The reverberation time affects how much sound energy bounces around the room, therefore affecting sound levels in the receiver room, which therefore affects the level difference from the sound source next door. The second test, is to measure background noise. If we’re measuring a high level of sound insulation then we might expect that background noise from other noise sources will be at a similar level to the level in the receiver room from our noise source next door, therefore we have to make a correction for this.

Putting these all together, the measurements of level difference, reverberation time, and background noise, enables us to calculate the result DnT,w + Ctr.

Impact sound insulation tests as alluded to earlier, are conducted using a ‘tapping’ machine. This machine is placed upon the floor and set to work, where the acoustic consultant will then move downstairs to measure in the room below. As per airborne sound tests, the acoustic engineer will measure reverberation time and background noise in the receiver room. Putting all this together enables the consultant to calculate the L’nT,w.

=== How many Sound Tests do I need? ===

In large scale residential developments, we’re going to have a certain level of repeatability. Do we need to test every single wall and floor? No. Lets say for example, we have a building containing 10 very similar flats, with the same constructions and construction detailing between them. For this, ADE indicates that we would only need 1 ‘set’ of tests, as it suggests that at least ‘one set of tests for every ten dwelling-houses, flats or rooms for residential purposes in a group or sub-group’.

So what defines a ‘set’ of tests?

{|
|width="100%"| Sets of tests in flats with a separating floor and a separating wall
|-
| [[File:Sound-Test-sets-1-no-text.jpg|1821px]]
|-
|
One set of tests should compromise 6 tests (4 airborne, 2 impact):

• 1 airborne test across a wall between (where possible) a pair of living rooms

• 1 airborne test across a wall between (where possible) a pair of bedrooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of living rooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of bedrooms
|}

{|
|width="50%"| [[File:Sound-Test-sets-2-no-text.jpg|300px]]
|width="50%"|
Sets of tests in flats with separating floors but without separating walls
One set of tests should compromise 4 tests (2 airborne, 2 impact):

• 1 airborne and 1 impact test across a floor between (where possible) a pair of living rooms

• 1 airborne and 1 impact test across a floor between (where possible) a pair of bedrooms
|}

{|
|width="100%"| Sets of tests in dwelling-houses with separating walls but no separating floors
|-
| [[File:Sound-Test-sets-3-no-text.jpg|1821px]]
|-
|
One set of tests should compromise 2 tests (2 airborne):

• 1 airborne test across a wall between (where possible) a pair of living rooms

• 1 airborne test across a wall between (where possible) a pair of bedrooms
|}

=== What condition should my site be in for Sound Testing? ===

Sound testing should ideally be conducted after completion of the building works, or as close to completion as possible. A failed acoustic test can often be down to constructions not being completed, penetrations and air gaps not being sealed, doors not being in place…

Your acoustic consultant will also ask for a bit of quiet. If you ask your acoustic engineer to come to site a few weeks before completion and there are still a lot of construction works and snagging going on, then the acoustic testing results may be adversely influenced by this noise.

Your acoustic consultant may thank you if you can provide 240v power on site. Whilst some acoustic engineers use battery-operated equipment, many don’t, and having to carry a transformer with an extension lead can mean that testing takes longer, which may mean more site visits, and therefore more cost for you.

Lastly, something that is often overlooked, is that impact sound insulation testing should be conducted in residential developments without the floor finish. A carpet floor finish is a very good dampener of impacts upon the floor. But in a few years, what if the occupant decides they would like to change this to hard flooring? Answer, the level of impact sound insulation could get much worse. Therefore to safeguard against this, impact sound insulation testing must be conducted without the floor finish (unless it can be argued that the finish is integral and cannot be changed later down the line). It’s for this reason that party floors usually have an acoustic/resilient underlay within the floor construction, or beneath the floor finish.

[https://www.parkerjonesacoustics.com/insights/articles/sound-testing-explained Article written and originally produced by ParkerJones Acoustics.]

Sound power

2019-12-09T17:53:23Z

ParkerJonesAcoustics:

The difference between sound pressure and sound power can be tricky to get your head around. For predicting noise levels from noise polluting sources like plant, it is very important.

Noise levels are often verbally quoted by non-acousticians with phrases like ‘this unit has a level of 60 dB’.

Unfortunately, based on that alone, one cannot do a great deal, without making a lot of assumptions. If the context is that the quoted level is 140 dB then there is of course a problem. But at 60 dB, depending on the situation, it’s difficult to assess the risk without digging into the information a little more.

What is a sound pressure level (SPL)?

A sound pressure is the pressure deviation from atmospheric pressure caused by a sound wave, in pascals. The sound pressure level (SPL) is a logarithmic measure of the ratio of a sound pressure over a reference sound pressure (corresponding to the hearing threshold of a young, healthy ear), quoted as a dB. If these two pressures are the same, we have an SPL of 0 dB.

A sound pressure level is what can physically be measured using a sound level meter. Most noise level parameters in a report are based upon an SPL, albeit they are mostly adjusted in some way, i.e. weighted to a single number (dB(A)), or a level difference such as a Dw.

A sound power level (SWL) is theoretical. A sound power is in Watts (W), a sound power level like above, is in dB, a logarithmic ratio of the sound power over a reference sound power. W for Watts, hence SWL (as SPL is already taken by sound pressure level!).

Why do we need sound power levels (SWL)?

The sound pressure level (SPL) depends on distance, the position of the source and the environment, i.e. reflections from the ground, or if inside, the surfaces of the room and therefore the reverberation time and volume of the room. So if one measures the SPL of a fan unit inside a plant room, and move this fan outside, the SPL is unlikely to be the same because of more sound energy escaping into the atmosphere. Similarly, if the unit is in the corner of a room, condensing sound radiation by the surfaces close around it, and then move this unit into the centre of the room on the floor, where it radiates more hemispherically, the SPL will be different. Simply moving further away from a sound source, will reduce the SPL, particularly noticeable when outside.

Take a large plant enclosure, with many different machines from different manufacturers. These manufacturers may all provide noise data as a sound pressure level. Same thing? Not quite. The issue is that all of these sound pressure levels could be measured at varying distances, some in a lab, some outside, some in an anechoic chamber (or very often not referencing how it was measured at all which is effectively useless data as it could be measured at 1m or 10m!). The data is just not consistent. Because of this, one has to make a lot of assumptions to predict the sum of noise levels from a plant enclosure, and most likely get it wrong.

The sound power level (SWL) helps around this consistency problem. It is not dependent on distance, position or environment. This is the crucial difference. It is a theoretical value; it is not directly measurable. A noise source will have the same sound power irrespective of where it is placed. It provides a level playing field to directly compare two sound sources. Predicting the noise levels from a plant enclosure is now much simpler, one can apply the same calculation to all of the equipment.

In summary, the SWL is very useful in quantifying how noisy a source is, like an extract fan or AHU, and therefore predicting the noise impact from a source in a new development, before it is built, without having to measure it. If you’re asked to provide noise data for something, your acoustician will always appreciate data which is given as a sound power level.

Can SWL be converted to SPL and vice versa?

Yes. The SWL is not directly measurable, but it is calculable from the SPL, and vice versa. So if one has sound power level data for a plant from the manufacturer, one can predict the noise level for that plant, in a room, outside, at 1m, at 10m, at 100m…and so on.

One thing to note, SPL is often written as Lp and SWL as Lw. With that in mind, a simple equation for calculating the direct component of SPL from SWL is given below:

[[File:Soundpowerequation.png]]

There are two variable terms here. Firstly r, is simply the distance in meters. The further away the 'receptor' is from the source, the less the sound pressure level.

[[File:Soundpressuredistance.png]]

Secondly, Q is the radiation pattern of the source. If one suspends a fan in the air it would radiate spherically. If placed on the floor, it now radiates hemispherically. Because the same SWL is now radiating into half the volume of before, the sound pressure energy condenses and therefore the SPL doubles. The fraction of this sphere gets smaller the more surfaces that are placed around it, as shown below. For each halving of the sphere, roughly add another 3 dB to the SPL. Hence if one measures an identical source placed in a corner, compared to one in the centre of the room, at the same distance, the former will be roughly 6 dB louder.

[[File:Soundpowerq.png]]

So now one can predict the noise levels that we hear and measure, from a multitude of different sources, at various distances and various positions. This all very useful in predicting the noise impact on the occupants of our development and the neighbouring properties.

What about noise levels inside a room?

The equation above concerns the ‘direct’ component of sound. This is the sound pressure received at our ears, directly from the source, without interacting with any objects or surfaces around us. In a room there are surfaces everywhere, reflecting sound towards our ears, the ‘reverberant’ component of sound. Hence the total energy is the sum of these two components. These calculations are something for a later article.

The direct equation best approximates sound propagation outside. But even then, the sound absorbing properties of the ground and the wind may affect the SPL over distance. You might notice the effect of the wind if you live or work a few hundred meters from a motorway. There is also the screening in noise levels from buildings or objects in between us and the source that obscure our view of it.

Article first published by [https://www.parkerjonesacoustics.com ParkerJones Acoustics] at [https://www.parkerjonesacoustics.com/insights/articles/sound-pressure-sound-power https://www.parkerjonesacoustics.com/insights/articles/sound-pressure-sound-power]

File:Soundpowerq.png

2019-12-09T17:52:00Z

ParkerJonesAcoustics:

File:Soundpressuredistance.png

2019-12-09T17:51:20Z

ParkerJonesAcoustics:

File:Soundpowerequation.png

2019-12-09T17:50:31Z

ParkerJonesAcoustics:

Sound power

2019-12-09T17:38:16Z

ParkerJonesAcoustics: Created page with "The difference between sound pressure and sound power can be tricky to get your head around. For predicting noise levels from noise polluting sources like plant, it is very impor..."

The difference between sound pressure and sound power can be tricky to get your head around. For predicting noise levels from noise polluting sources like plant, it is very important.

Noise levels are often verbally quoted by non-acousticians with phrases like ‘this unit has a level of 60 dB’.

Unfortunately, based on that alone, one cannot do a great deal, without making a lot of assumptions. If the context is that the quoted level is 140 dB then there is of course a problem. But at 60 dB, depending on the situation, it’s difficult to assess the risk without digging into the information a little more.

What is a sound pressure level (SPL)?

A sound pressure is the pressure deviation from atmospheric pressure caused by a sound wave, in pascals. The sound pressure level (SPL) is a logarithmic measure of the ratio of a sound pressure over a reference sound pressure (corresponding to the hearing threshold of a young, healthy ear), quoted as a dB. If these two pressures are the same, we have an SPL of 0 dB.

A sound pressure level is what can physically be measured using a sound level meter. Most noise level parameters in a report are based upon an SPL, albeit they are mostly adjusted in some way, i.e. weighted to a single number (dB(A)), or a level difference such as a Dw.

A sound power level (SWL) is theoretical. A sound power is in Watts (W), a sound power level like above, is in dB, a logarithmic ratio of the sound power over a reference sound power. W for Watts, hence SWL (as SPL is already taken by sound pressure level!).

Why do we need sound power levels (SWL)?

The sound pressure level (SPL) depends on distance, the position of the source and the environment, i.e. reflections from the ground, or if inside, the surfaces of the room and therefore the reverberation time and volume of the room. So if one measures the SPL of a fan unit inside a plant room, and move this fan outside, the SPL is unlikely to be the same because of more sound energy escaping into the atmosphere. Similarly, if the unit is in the corner of a room, condensing sound radiation by the surfaces close around it, and then move this unit into the centre of the room on the floor, where it radiates more hemispherically, the SPL will be different. Simply moving further away from a sound source, will reduce the SPL, particularly noticeable when outside.

Take a large plant enclosure, with many different machines from different manufacturers. These manufacturers may all provide noise data as a sound pressure level. Same thing? Not quite. The issue is that all of these sound pressure levels could be measured at varying distances, some in a lab, some outside, some in an anechoic chamber (or very often not referencing how it was measured at all which is effectively useless data as it could be measured at 1m or 10m!). The data is just not consistent. Because of this, one has to make a lot of assumptions to predict the sum of noise levels from a plant enclosure, and most likely get it wrong.

The sound power level (SWL) helps around this consistency problem. It is not dependent on distance, position or environment. This is the crucial difference. It is a theoretical value; it is not directly measurable. A noise source will have the same sound power irrespective of where it is placed. It provides a level playing field to directly compare two sound sources. Predicting the noise levels from a plant enclosure is now much simpler, one can apply the same calculation to all of the equipment.

In summary, the SWL is very useful in quantifying how noisy a source is, like an extract fan or AHU, and therefore predicting the noise impact from a source in a new development, before it is built, without having to measure it. If you’re asked to provide noise data for something, your acoustician will always appreciate data which is given as a sound power level.

Can SWL be converted to SPL and vice versa?

Yes. The SWL is not directly measurable, but it is calculable from the SPL, and vice versa. So if one has sound power level data for a plant from the manufacturer, one can predict the noise level for that plant, in a room, outside, at 1m, at 10m, at 100m…and so on.

One thing to note, SPL is often written as Lp and SWL as Lw. With that in mind, a simple equation for calculating the direct component of SPL from SWL is given below:

[[File:0?e=1580342400&v=beta&t=23WxIF8oycfyE9YKW2yhFVdvjBG6LyjCEwGLd9oBcuU]]

There are two variable terms here. Firstly r, is simply the distance in meters. The further away the 'receptor' is from the source, the less the sound pressure level.

[[File:0?e=1580342400&v=beta&t=Ah0kk69zQasO5svrggebLWtTTeTCEhSGyJxHLeYlPqw]]

Secondly, Q is the radiation pattern of the source. If one suspends a fan in the air it would radiate spherically. If placed on the floor, it now radiates hemispherically. Because the same SWL is now radiating into half the volume of before, the sound pressure energy condenses and therefore the SPL doubles. The fraction of this sphere gets smaller the more surfaces that are placed around it, as shown below. For each halving of the sphere, roughly add another 3 dB to the SPL. Hence if one measures an identical source placed in a corner, compared to one in the centre of the room, at the same distance, the former will be roughly 6 dB louder.

[[File:0?e=1580342400&v=beta&t=61tRoEI3iKMQ-UOec4QEvdyw_hreCri1vaxyALk2Szs]]

So now one can predict the noise levels that we hear and measure, from a multitude of different sources, at various distances and various positions. This all very useful in predicting the noise impact on the occupants of our development and the neighbouring properties.

What about noise levels inside a room?

The equation above concerns the ‘direct’ component of sound. This is the sound pressure received at our ears, directly from the source, without interacting with any objects or surfaces around us. In a room there are surfaces everywhere, reflecting sound towards our ears, the ‘reverberant’ component of sound. Hence the total energy is the sum of these two components. These calculations are something for a later article.

The direct equation best approximates sound propagation outside. But even then, the sound absorbing properties of the ground and the wind may affect the SPL over distance. You might notice the effect of the wind if you live or work a few hundred meters from a motorway. There is also the screening in noise levels from buildings or objects in between us and the source that obscure our view of it.

Article first published at [https://www.parkerjonesacoustics.com/insights/articles/sound-pressure-sound-power https://www.parkerjonesacoustics.com/insights/articles/sound-pressure-sound-power]

User:ParkerJonesAcoustics

2019-12-09T17:24:53Z

ParkerJonesAcoustics:

Acoustics, Noise and Vibration Consultancy based in the South West, working around the UK.

We work across [https://www.parkerjonesacoustics.com/sectors all areas of acoustics] in the built environment, industry, infrastructure, power and mining/minerals.

Need a [https://www.parkerjonesacoustics.com/services/noise-surveys noise survey], a sound test, vibration monitoring or any aspect or acoustics/noise/vibration design from feasibility, through planning, through detailed design, construction and completion, [https://www.parkerjonesacoustics.com/contact-us then give us a call.]

Our biggest specialism in the detailed acoustic design of residential, educational and healthcare buildings.

[https://www.parkerjonesacoustics.com https://www.parkerjonesacoustics.com]

chris@parkerjonesacoustics.com

01179146558

User:ParkerJonesAcoustics

2019-12-09T17:23:10Z

ParkerJonesAcoustics:

Acoustics, Noise and Vibration Consultancy based in the South West, working around the UK.

We work across all areas of acoustics in the built environment, industry, infrastructure, power and mining/minerals.

Need a noise survey, a sound test, vibration monitoring or any aspect or acoustics/noise/vibration design from feasibility, through planning, through detailed design, construction and completion, then give us a call.

Our biggest specialism in the detailed acoustic design of residential, educational and healthcare buildings.

[https://www.parkerjonesacoustics.com https://www.parkerjonesacoustics.com]

chris@parkerjonesacoustics.com

01179146558

Rw and Dw/DnTw in Acoustics - What do they mean?

2019-08-11T20:57:25Z

ParkerJonesAcoustics: Created page with "The aim of this article is to hopefully shed some light on the 'dark art' of acoustics for clients and design teams, without going too far into the mathematics and every nitty gr..."

The aim of this article is to hopefully shed some light on the 'dark art' of acoustics for clients and design teams, without going too far into the mathematics and every nitty gritty technicality behind the design process, that us acousticians love to get stuck into.

Dw is a term that relates to onsite sound insulation. It is as simple as the noise level in my source room, minus the noise level in my receiver room, the level difference. This is a performance standard, a value you can physically measure on site after completion, and often have to to demonstrate compliance with building regulations for schools and residential developments, and to achieve BREEAM credits.

The sound transmission between two rooms is the sum of many paths. The dominant and obvious path, is directly through the separating partition. However sound also transmits through junctions with the floor, soffit, facade and corridor wall. For example if a wall is only built to the underside of a ceiling, and not to the slab, a significant flanking path around the wall exists. Flanking through mechanical ducts, services routes and penetrations and pipes and steels running between rooms also need to be considered. Flanking is particularly important to control on high performance walls, the margin for error rapidly decreases around rooms such as music and performing arts spaces.

You may hear variations of Dw, for example BB93 and HTM specifies DnTw for schools and healthcare buildings. The nT in DnTw is the normalisation of reverberation, which allows us to compare sound insulation results objectively on a level field, irrespective of differences in reverberation. Part E for residential uses DnTw + Ctr, the Ctr being a low frequency correction, making this target more onerous than a DnTw. A Dw is also referred to in BREEAM documents for the performance targets of other building types, and is the term that most effectively follows the subjective level of sound insulation heard on site, though most standards will use the normalised version. The important thing to remember, is that these are all onsite performance targets.

Rw relates to the laboratory rated sound reduction index of a single element, i.e. a wall. A laboratory test measures the wall performance in isolation from any other sound flanking paths. So if you were to build a 50 dB Rw wall, in a perfect building with infinitely high mass surrounding constructions with no flanking whatsoever, it could theoretically achieve 50 dB Dw on site. Of course, we cannot build perfect buildings, and therefore we have to account for flanking. We also cannot guarantee that the Rw was determined correctly, or that the element tested in a lab was of a much different surface area to our actual element, but this is a topic for another day.

The important thing is, we need to choose walls, floors, glazing and doors with a sufficient Rw rating, and then build these well through good detailing and adequate workmanship, to achieve our onsite Dw, DnTw, or DnTw + Ctr targets.

=== How do I get from Dw to Rw? ===

The same construction measured in a lab will get the same Rw result every time. But when measured on-site, the result will vary from room to room, project to project.

The calculation to convert from Rw to Dw has to account for:

* The area size of the separating partition, a bigger wall means more area of sound energy to transmit through. Bigger area = Higher Rw.
* The volume of the 'receiving' room. The smaller the space, the great the concentration of sound energy, the higher the sound pressure level. Smaller volume = Higher Rw.
* The reverberation time of the ‘receiving’ room, which is the time taken for sound to decay. A sports hall or church, with a large volume and hard reflective surfaces such as concrete or plasterboard, has a long reverberation time. A small space with lots of soft absorbent materials such as ceiling tiles, acoustic wall panels or soft furnishings, will have a low reverberation time. A high reverberation time means a build up in noise levels from sound reflecting around the room, with energy being dissapated slowly from a lack of absorbent materials. Higher reverberation time = Higher Rw.
* Account for potential flanking transmission on-site due to a potential downfall in construction quality or inattention in design to junction and penetrating detailing.

Therefore it is not a simple case of Rw = Dw + X dB. The Rw can vary significantly between partitions, even if they require the same Dw. The image below shows this. If we look at DnTw, or DnTw + Ctr, theoretically the DnTw on site should not change with reverberation time (RT), as the nT refers to the normalisation of reverberation. The DnTw allows us to compare sound insulation results objectively on a level field, irrespective of reverberation. However calculation methods in standards like BB93 still use RT within the formula to calculate Rw from DnTw. The RT still effects the Dw, which is the true level difference, the one we subjectively hear on site!

[[File:Rw vs Dntw.jpg]]

=== How does this help my design? ===

The temptation by some consultants is to simply say 'Rw = Dw + 8 dB'. Why? This is a comfortable safety margin, and avoids the time consuming exercise of measuring each wall, volumes of each room and calculating the Rw.

So what's wrong with this? Clearly we see from the illustration above, if the same wall type Rw (say 48 dB) is used everywhere where the Dw is 40 dB, there will be rooms that fail, as well as rooms that exceed the required performance standard by some distance. So not only will I have walls in my building that fail and may require expensive remedial work, I may have overspent unnecessarily on the walls that pass. If we just take the worst case at 53 dB Rw and minimise the risk of failure, then most of the walls will be over designed.

Therefore doing these calculations correctly, wall by wall, and paying close attention to the construction details, is important in achieving a successful, cost effective design.

Of course we don't want to end up with 99 different wall types. But if we carefully design the construction details, limit the number of plasterboard types and convey this clearly to the site team, we can cut down on safety margins and use a handful of wall types.

Reducing every dB of overdesign quickly sums up when applying over projects, schemes and larger frameworks, particularly those with common shared constructions. And of course, simply getting things right in the first place cuts down on costly post construction remedial work!

I hope you enjoyed this short article, and keep an eye out for more articles on the common questions that I get asked by clients in my job as an acoustic consultant. Feel free to connect and message me through [https://www.linkedin.com/in/chrisjonesacoustician/ LinkedIn], the [https://www.parkerjonesacoustics.com ParkerJones Acoustics website] (opening October 2019), or emailing chris@parkerjonesacoustics.com

[[Category:Education]] [[Category:Design]]

File:Rw vs Dntw.jpg

2019-08-11T20:55:03Z

ParkerJonesAcoustics: Diagram showing how Rw is calculated from Dw/Dntw in Acoustics, relating to sound insulation.

Diagram showing how Rw is calculated from Dw/Dntw in Acoustics, relating to sound insulation.

File:ParkerJones Acoustics - Our Services - Feasibility, Planning and Detailed Design.pdf

2019-07-22T21:24:21Z

ParkerJonesAcoustics: Our Services through RIBA Stages 1 to 4 - Feasibility, Planning and Detailed Design.

Our Services through RIBA Stages 1 to 4 - Feasibility, Planning and Detailed Design.