Why is removing hearing protection for short periods bad?

I am regretting writing this page already and I've only got as far as the title and first line. How to explain this without going off into boring nerdy noise-speak while having it still make sense...

One of the important things to cover when issuing hearing protection and training people in how to use it is getting them to realise they cannot keep removing it to talk to people while in a high noise area, even if only for a few minutes. If they do this has a dramatic effect on their noise exposures, but can be hard to get across to them why. 

How removing hearing protection changes noise exposures

To keep the maths simple, let’s start off with a person who works in an area where the noise levels are a constant 100dB throughout their eight hour working day. Loud but not unrealistically so. They wear hearing protection and under the protector experience a noise level of a constant 75dB. That's perfect and not unreasonable for real-world use of an ear plug.

They occasionally talk to other people while in the high noise area and throughout the day remove their hearing protection three times for no more than five minutes at a time. This means they are wearing hearing protection for 7 hours and 45 minutes and no hearing protection for 15 minutes.

Removing hearing protection changes their daily exposure to a combination of:

  • 7 hours and 45 minutes at 75dB, and

  • 15 minutes at the full 100dB.

Because of the ridiculously complicated way noise is measured, 100dB(A) for 15 minutes is the same as 85dB(A) for eight hours, even if the rest of the day was spent in silence. Think of it as all the noise rushing in at once over the 15 minutes rather than trickling in over eight hours.

This means that by removing their hearing protection for merely 15 minutes they have changed their daily exposure from 75dB(A) to 85dB(A), and are now in the area where noise is known to damage hearing. If they do this regularly they will start to suffer hearing losses.

Reasons given for it

When asked, the reasons given for removing hearing protection for short periods usually all come down to saying they need to do it so they can hear what someone is saying, but this is more about perception than reality.

Without hearing protection, what they are hearing is a large amount of background noise, then speech on top of that, with the important bit they are actually listening to being the small difference between the two - that's the part people focus on to pick out the speech over the machinery noise. 

With hearing protection everything gets quieter, but that all-important gap between machinery noise and speech stays pretty much the same, meaning the gap between the two noises which they are actually listening to stays the same, meaning hearing protection has no impact on the ability to pick speech out above background noise levels.

Anecdotally, the sites where I have had the comments about not being able to hear speech are always ones where either the hearing protection is new, or it's use and enforcement is somewhat variable. Conversely, in sites where hearing protection is always used without question  I pretty much never get complains about hearing speech and needing to remove the protector to communicate. The issue is largely one of perception.

Technical solutions

If noise levels are uncommonly loud there are technical solutions available, from the fairly cheap ones like the Peltor Optime Push-to-Listen ear defenders, which I have used for years, through to more expensive units which have built-in radio communications.

The Push-to-Listen has a button which lets just some of the key speech frequencies through for a short time and can improve understanding of speech, without compromising the integrity of the protection given. Not bad for about £28.