Exhibition sound level

Professional Definition

Exposure sound level ($L_{AE}$) is the A-weighted sound level of a single acoustic event, determined by the formula:

Component parameters:

• pA(t) – instantaneous value of the acoustic pressure corrected for the A-frequency characteristic [Pa].

• p0 – reference pressure equal to 20 µPa (micropascals).

• T0 – reference time equal to 1 second.

• t2 - t1 – time interval from the beginning to the end of the event.

In acoustic engineering, SEL is essential because it allows for fair comparisons of events with completely different time characteristics, e.g., a sudden gunshot and a prolonged pass of a helicopter.

Acoustics in Simple Words

Imagine that noise is water poured from a bucket.

1. Short impulse (e.g., slamming a door): You pour out the whole bucket of water in a fraction of a second – the stream is very strong but disappears almost immediately.

2. Long sound (e.g., passing train): You pour the same bucket slowly, steadily, and thinly for a whole minute.

SEL (LAE) does not measure how forcefully the water splashed in a given second. This parameter tells us: how much water has been poured out in total.

Intuition: What if we took all the energy from the long passage of a train and "compressed" it so that it lasted only one second, how loud would it be? That’s what the exposure level tells us.

Summary

• Energy, not just loudness: LAE measures the total dose of energy delivered by the event.

• Comparability: By reducing each sound to 1 second, we can objectively assess what is more disruptive: a series of short taps or one long noise.

• Application: This is a fundamental parameter in creating acoustic maps and assessing aviation, railway, and industrial noise.