Doubling up on hearing protection

Wearing double hearing protection at work.

A common recommendation I have seen from Occupational Health Physicians has been ‘recommend wear double hearing protection’. What they are saying is that they recommend the person concerned wears two sets of hearing protection, usually a plug and a muff over the top, but to be honest, it is nonsense and usually has no link to the findings of the noise assessment.

Is the noise too much for hearing protection?

The only reason to wear double hearing protection would be because the person is still at a risk of excess noise despite wearing hearing protection, but how realistic is this?

EARsoft FX plugs

The strongest hearing protection on the market has an SNR of 39dB and all the ones at this levels are foam plugs. (Yes indeedy, another myth busted there - ear muffs are not stronger than ear plugs, the strongest hearing protection are all plugs).

Take the E-A-RSoft FX ear plug, a soft squishy plug with an SNR of 39dB. The HSE say the safe level under a hearing protector is less than 85 dB(A), so let’s use that 85 dB(A) figure.

To work out the noise level under a hearing protector you take the noise level, subtract the SNR of the protector, and then allow 4dB for some real-world slightly incorrect usage. That means the foam plugs with an SNR of 39dB are good for noise levels up to 120dB. (The noise level of 85, plus the 39 of the protector, minus that 4dB). That is an average of 120 dB for eight hours.

In 30 years of doing noise assessments I have never once come across a workplace with an average noise level of 120dB(A) for a continual eight hours or even anything remotely close to that. An occasional peak that high, sure, but not a continual level.

Even if we give more leeway and work on a level of 80 dB(A) under the protector rather than 85, that still gives us a safe working environment of up to 115 dB(A), again an average level I have never seen.

So that means the strongest type of ear plug on the market is more than good enough for pretty much every workplace out there.

Too much hearing protection

Wearing two sets of ear muffs

Indeed, in noise assessment the opposite is true, in 3/4 of all the noise assessments I do, the most common finding is the hearing protection is too strong for the noise risk present, not too weak.

Too much hearing protection is itself a problem. People get too isolated to they start to take the protection off to talk to people and end up with less protection than if they’d just had a weaker hearing protector in the first place.

They also start to be unable to hear things like forklifts moving around, or cannot hear alarms or machinery noise. A lot of experienced people use how a machine sounds to know it is running as it should be. Double protection stops that, so they remove it.

Recommended on the basis of ignorance

I don’t mean that as a personal thing, I mean that Occupational Health Physician recommendations of double hearing protection are almost always made in complete ignorance of the facts of the workplace. They don’t know what the noise levels are and they don’t know what the hearing protection has been assessed as in the noise assessment.

I have personal experience of this. I had a case where an Occupational Health Physician recommended one chap had double hearing protection as he was showing some issues in his hearing. However, I myself had done the noise assessment there and I knew for a fact the hearing protection in use was already way too strong for the noise risk present. Worn properly it was reducing noise levels to about 59dB, far too much. (59dB is very quiet - think quiet warehouse where nothing is happening except a wee bit of ventilation, that’s about 59dB(A) or so). Adding another layer of protection on top of that gave no benefit to their hearing whatsoever.

Some people are more susceptible to noise damage than others, granted, but there is still a massive gap between the levels of noise they would experience under the more powerful hearing protectors on the market and any level of noise which is going to damage hearing.

The impact of doubling protection is over-estimated

You’re just going to have to go with me on this, but… Decibels were invented by a fella who was clearly off his head on something extremely hallucinogenic as they make no sense at all. One component is that 3dB is doubling the noise energy, and conversely, a drop of 3dB is halving the noise.

So if you have a hearing protector which reduces the noise by say 30dB, and then you add a second layer of protection which also reduces the noise by 30dB, the combined reduction is not 60dB, but is 33dB.

See, I told you to just go with me on it.

What that means is that doubling up on the protection is not only completely unnecessary, but it doesn’t have that big an impact either. It manages to be both pointless and also rather ineffective.

Summary on double hearing protection

The strongest hearing protectors on the market are already too strong for pretty much every workplace out there meaning there is a suitable hearing protector for every noise exposure without wearing two sets of hearing protection.

Doubling up on hearing protection is almost always incorrect, and a recommendation made in ignorance of the basic facts and findings of a noise assessment.

It can range from pointless to actually increasing risk by encouraging reduced compliance.

Occupational Health Physicians have some uses, but in 30 years of workplace noise safety including both noise assessments and hearing testing, I have not seen one recommendation for double hearing protection which was actually justified by the noise exposure levels on a site.