# Equivalent Continuous Sound Level

The steady state dB(A) level which would produce the same A-weighted sound energy over a stated period of time as a specified time-varying sound.

Equivalent continuous A-weighted sound pressure level is widely used around the world as an index for noise. It is defined as "the A-weighted sound pressure level of a noise fluctuating over a period of time T, expressed as the amount of average energy." It is expressed as:

where
LAeq = equivalent continuous A-weighted sound pressure level [dB]
p0 = reference pressure level = 20µPa
pA= A-weighted pressure [Pa]
t1 = start time for measurement [s]
t2 = end time for measurement [s]

If we wanted to calculate the equivalent continuous A-weighted sound pressure level from the sound exposure level of a number of discrete events such as a train passing then we can use the follwing equation:

: Time (sec) targeted for LAeq. From 07:00 to 22:00 is 54,000 sec. From 22:00 to 07:00 is 32,400 sec.

Subjects: Audio Noise & Vibration