What’s the importance of LAeq in sound measurement?


I’ve been playing around with the NIOSH SLM app on my phone. It’s an app that measures sound levels to make sure they’re safe. One of the things it measures is LAeq. I’ve tried to figure out what that’s measuring both in the app and on Google but none of the answers I get have been straightforward. It says “equivalent (averaged every second) continuous sound level in A-weighted decibels dB(A)”. I’m struggling to understand precisely what it means by that. Is this just an average of the decibel level in the given time, or is there more to it? Why would I want to measure this otherwise? And what is a safe reading for LAeq?

In: 4

iiuc: Level A weighted eq (LAeq) is a way to measure sound that emphasizes sound frequencies in the range that humans hear best. It also de-emphasizes very high frequency and very low frequency sound at the edge or outside of human hearing range.

This is because the sound frequencies that we hear best sound the loudest to us and sounds frequencies at the edges of our hearing range don’t sound as loud even if both are the same volume. So by using LAeq we get a reading that’s more in line with what we are actually experiencing.

Example: if I played a high pitch sound, a mid pitch sound, and a low pitch sound at the same volume, the middle pitch sound would seem loudest to us. But if we measured with an unweighted (LZeq) audio meter they would all appear the same.

LAeq measures sound closer to the way we hear it.

You want the average noise if you’re talking about safe noise levels because if you were to just take a noise reading over twenty minutes and report the highest reading, it wouldn’t give an accurate account of overall noise exposure. If someone walks by and screams for a second, yes that will be a very high reading, but overall noise exposure averaged over the hour or twenty minutes would not be as high and would be a more accurate measure of exposure.

As for the “A Weighting”, sound (noise is just what would be considered excess sound) consists of a whole spectrum of frequencies of sound waves. The human ear, though, can only hear some of these frequencies, and of those, can hear some better than others. The “A Weighting” takes all the frequencies the noise meter (in this case your phone using the app) and does a weighted average to approximate what the human ear is actually hearing of the all the sound recorded.