Designing Buildings - User contributions [en]

Reverberation in buildings

2013-11-28T13:08:09Z

MACH Acoustics:

= Introduction =

The reverberation time of a room is defined as the time it takes for sound to decay by 60 dB after an abrupt termination. The reverberation time of a room is linked to the total quantity of soft treatments and the volume of the room by the Sabine equation;

RT = Volume x 0.161 / Total Acoustic Absorption

[[File:Reverberation.jpg|800x399px|alt=Reverberation.jpg]]

Image: To control reverberation time, acoustic absorption is used.

Room acoustics / reverberation affects the way a space sounds. A high reverberation time can make a room sound loud and noisy. Speech intelligibility is also a function of reverberation, a high reverberation time causes speech to sound muffled and muddy. Rooms designed for speech therefore typically have a low reverberation time: ≤1 second. A high reverberation time can enhance a music hall by adding richness, depth and warmth to music. A higher level of reverberation within a concert hall is therefore critical.

The illustration below provides indicative reverberation times for a range of building types and room volumes.

[[File:Indicative reverberation times.jpg|800x299px|alt=Indicative reverberation times.jpg]]

= Acoustic properties of materials =

To control reverberation time, acoustic absorption is used. Absorbent materials conventionally take two forms; fibrous materials or open-celled foam. Fibrous materials absorb sound as sound waves force the fibres to bend and this bending of the fibres generates heat. The conversion of acoustic energy into heat energy results in the sound effectively being absorbed. In the case of open celled foam, the air movement resulting from sound waves pushes air particles through the narrow passages which in turn generate a viscous loss along with heat.

Architecturally, fibrous materials and open celled foams are not particularly attractive or robust. It is therefore common to cover these materials with an acoustically transparent finish such as a tissue, cloth or slatted wood, or perforated materials such as wood, metal, plasterboard and so on.

The thickness of a given material along with properties such as its fibrousity governs its acoustic performance. Finishes within a space are defined in terms of their absorption coefficient. This is a number between 0.0 (100% reflective) for example stone, tiles or concrete and 1.0 (100% absorbent), for example high performance acoustic ceiling tiles, slabs of mineral wool, etc. Products such as carpets typically have an absorption coefficient between 0.1 and 0.3 depending on their thickness. Perforated plasterboard generally provides around 0.6 to 0.7.

It is also common to classify absorbent materials in categories, A to E, where A is highly absorbent and E is almost fully reflective.

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This article was created by --[[User%3AMACH%20Acoustics|MACH Acoustics]] 11:04, 28 November 2013 (UTC)

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Sound insulation.

=== External references ===
*MACH Acoustics: [http://www.machacoustics.com/sustainableacoustics/room-acoustics-reverberation Room acoustics and reverberation].

Reverberation in buildings

2013-11-28T13:07:25Z

MACH Acoustics:

= Introduction =

The reverberation time of a room is defined as the time it takes for sound to decay by 60 dB after an abrupt termination. The reverberation time of a room is linked to the total quantity of soft treatments and the volume of the room by the Sabine equation;

RT = Volume x 0.161 / Total Acoustic Absorption

[[File:Reverberation.jpg|800x399px|alt=Reverberation.jpg]]

Image: To control reverberation time, acoustic absorption is used.

Room acoustics / reverberation affects the way a space sounds. A high reverberation time can make a room sound loud and noisy. Speech intelligibility is also a function of reverberation, a high reverberation time causes speech to sound muffled and muddy. Rooms designed for speech therefore typically have a low reverberation time: ≤1 second. A high reverberation time can enhance a music hall by adding richness, depth and warmth to music. A higher level of reverberation within a concert hall is therefore critical.

The illustration below provides indicative reverberation times for a range of building types and room volumes.

[[File:Indicative reverberation times.jpg|800x299px|alt=Indicative reverberation times.jpg]]

= Acoustic properties of materials =

To control reverberation time, acoustic absorption is used. Absorbent materials conventionally take two forms; fibrous materials or open-celled foam. Fibrous materials absorb sound as sound waves force the fibres to bend and this bending of the fibres generates heat. The conversion of acoustic energy into heat energy results in the sound effectively being absorbed. In the case of open celled foam, the air movement resulting from sound waves pushes air particles through the narrow passages which in turn generate a viscous loss along with heat.

Architecturally, fibrous materials and open celled foams are not particularly attractive or robust. It is therefore common to cover these materials with an acoustically transparent finish such as a tissue, cloth or slatted wood, or perforated materials such as wood, metal, plasterboard and so on.

The thickness of a given material along with properties such as its fibrousity governs its acoustic performance. Finishes within a space are defined in terms of their absorption coefficient. This is a number between 0.0 (100% reflective) for example stone, tiles or concrete and 1.0 (100% absorbent), for example high performance acoustic ceiling tiles, slabs of mineral wool, etc. Products such as carpets typically have an absorption coefficient between 0.1 and 0.3 depending on their thickness. Perforated plasterboard generally provides around 0.6 to 0.7.

It is also common to classify absorbent materials in categories, A to E, where A is highly absorbent and E is almost fully reflective.

----

This article was created by --[[User%3AMACH%20Acoustics|MACH Acoustics]] 11:04, 28 November 2013 (UTC)

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Sound insulation.

=== External references ===
*MACH Acoustics: [http://www.machacoustics.com/sustainableacoustics/sound-insulation Subjective Evaluation and Conversion between RW and DW].

Sound insulation in buildings

2013-11-28T13:06:31Z

MACH Acoustics:

= 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 specifes 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|711x880px|alt=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 fnal site requirements, Dw levels are specifed by clients and Building Regulations. Rw represents the lab tested sound insulation of an element making up a partition wall/foor type. Due to fanking and other factors, lab rated sound reduction levels will not be achieved on-site. Conventionally, there is a 5 to 10 dB reduction between a Rw lab tested fgure and an on-site Dw fgure. 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.

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

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Reverberation

=== External references ===
*MACH Acoustics: [http://www.machacoustics.com/sustainableacoustics/sound-insulation Subjective Evaluation and Conversion between RW and DW].

User:MACH Acoustics

2013-11-28T13:04:09Z

MACH Acoustics:

MACH Acoustics provide acoustic consultancy across all areas of the built environment. We deliver intelligent, original and cost effective acoustic solutions, which achieve our clients' goals. We are committed to sustainable design and through experience and R&D, we are confident that we can achieve natural / cross ventilation across all sites and developments.

Articles on Designing Buildings Wiki by MACH Acoustics include:

*[[Reverberation|Reverberation]].

*[[Sound_insulation|Sound insulation]].

Reverberation in buildings

2013-11-28T11:04:16Z

MACH Acoustics:

= Introduction =

The reverberation time of a room is defined as the time it takes for sound to decay by 60 dB after an abrupt termination. The reverberation time of a room is linked to the total quantity of soft treatments and the volume of the room by the Sabine equation;

RT = Volume x 0.161 / Total Acoustic Absorption

[[File:Reverberation.jpg|800x399px|alt=Reverberation.jpg]]

Image: To control reverberation time, acoustic absorption is used. Absorbent materials conventionally take two forms; fibrous materials or open celled foam.

Room acoustics / reverberation affects the way a space sounds. A high reverberation time can make a room sound loud and noisy. Speech intelligibility is also a function of reverberation, a high reverberation time causes speech to sound muffled and muddy. Rooms designed for speech therefore typically have a low reverberation time: ≤1 second. A high reverberation time can enhance a music hall by adding richness, depth and warmth to music. A higher level of reverberation within a concert hall is therefore critical.

The illustration below provides indicative reverberation times for a range of building types and room volumes.

[[File:Indicative reverberation times.jpg|800x299px|alt=Indicative reverberation times.jpg]]

= Acoustic properties of materials =

To control reverberation time, acoustic absorption is used. Absorbent materials conventionally take two forms; fibrous materials or open-celled foam. Fibrous materials absorb sound, since sound waves force the fibres to bend and this bending of the fibres generates heat. The conversion of acoustic energy into heat energy results in the sound effectively being absorbed. In the case of open celled foam, the air movement resulting from sound waves pushes the air particles through the narrow passages which in turn generate a viscous loss along with heat.

Architecturally, fibrous materials and open celled foams are not particularly attractive or robust. It is therefore common to cover these materials with an acoustically transparent finish such as a tissue, cloth, slatted wood, or perforated materials such as wood, metal, plasterboard and so on.

The thickness of a given material along with properties such as its fibrousity governs itsacoustic performance. Finishes within a space are therefore defined in terms of their absorption coefficient. This is a number between 0.0 (100% reflective) for example stone, tiles or concrete and 1.0 (100% absorbent), for example high performance acoustic ceiling tiles, slabs of mineral wool, etc.

Products such as carpets typically have an absorption coefficient between 0.1 and 0.3 depending on their thickness. Perforated plasterboard generally provides around 0.6 to 0.7.

It is also common to classify absorbent materials in categories, A to E, where A is highly absorbent and E is almost fully reflective.

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This article was created by --[[User:MACH Acoustics|MACH Acoustics]] 11:04, 28 November 2013 (UTC)

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