Last edited 16 Feb 2021

Equivalent continuous sound pressure level

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.

The term ‘equivalent continuous sound pressure level’ refers to:

An index used internationally for the assessment of environmental sound impacts. It is defined as the notional unchanging level that would, over a given period of time (T), deliver the same sound energy as the actual time-varying sound over the same period. Hence fluctuating sound levels can be described in terms of an equivalent single figure value.

It is expressed as:

Equivalent continuous sound pressure level.png

Ref The HS2 London-West Midlands Environmental Statement, published by the Department for Transport in November 2013.

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