Paragraph 3 Calculation of sound exposure level LAE from measured noise data

The sound exposure level L_AE is defined as the level, in decibels, of the time integral of squared ‘A’-weighted sound pressure (P_A) over a given time period or event, with reference to the square of the standard reference sound pressure (P_o) of 20 micropascals (P) and a reference duration of one second.

This unit is defined by the expression—

where T_o is the reference integration time of one second and (t₂ - t₁) is the integration time interval.

The above integral can also be expressed as—

where L_A(t) is the time varying ‘A’-weighted sound level.

The integration time (t2 - t1) in practice must not be less than the time interval during which LA(t) first rises to within 10dB(A) of its maximum value (LAmax) and last falls below a level of 10dB(A) less than its maximum value.

The L_AE may be approximated by the following expression for L_Amax—

where ΔA is the duration allowance given by ΔA = 10 log τ where τ = (t₂-t₁)/2.