Last edited 21 Jan 2019

Sound exposure level

Sound exposure level is the sound level at a receptor which, if maintained at a constant level for a period of one second, would have the same amount of energy as a given event (of any duration) at the same receptor.

The sound power level (Lw) of a source is a measurement of the total acoustic power it radiates. The sound power level is an intrinsic characteristic of a source (analogous to its volume or mass), which is not affected by the environment within which the source is located.

Sound pressure level is the parameter by which sound levels are measured in air. It is measured in decibels. The threshold of hearing has been set at 0dB, while the threshold of pain is approximately 120dB. Normal speech is approximately 60dB at a distance of 1 metre and a change of 3dB in a time varying sound signal is commonly regarded as being just detectable. A change of 10dB is subjectively twice, or half, as loud. (See also Equivalent continuous sound pressure level)

Ref The HS2 London-West Midlands Environmental Statement, Glossary of terms and list of abbreviations, DETR 2013.

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