# 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
*L*= equivalent continuous A-weighted sound pressure level [dB]_{Aeq}*p*= reference pressure level = 20_{0}*µ*Pa*p*= A-weighted pressure [Pa]_{A}*t*= start time for measurement [s]_{1}*t*= end time for measurement [s]_{2}

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 L_{Aeq}. From 07:00 to 22:00 is 54,000 sec. From 22:00 to 07:00 is 32,400 sec.

**See also: **Community Noise Criteria, Weighted Equivalent Continuous Perceived Noise Level.

**Subjects: ** Audio Noise & Vibration