Effect of noise on hearing

Or to put it another way, 'why employees should give a damn about this'.

Risk versus inevitability

One part to highlight for the ever-jaded employee all too used to hearing about 'risk' and 'chances of an injury' is that in high noise exposures they can pretty much forget about 'risk'. It's not like manual handing where someone may do the job for five years and have a knackered back whereas someone else may do it for 40 years and be absolutely fine, in high noise exposures they will have a problem, it's just a question of how much of a problem.

As the ears respond physically to noise it is like all physical things, and some can take more of it than others, but with repeated exposures everyone will start to suffer. 

How the ear responds to noise

Physical hearing

Before describing what effect noise has on hearing it's worth trying detail, mercifully briefly, how ears actually respond to noise. Here is the 'totally striped down but still accurate' guide to what noise does in your ears:

  1. The ear has tiny microscopic hairs deep inside it which physically vibrate in response to noise.
  2. Each person starts off with about 10,000 of them at birth. 
  3. They do not heal or recover when damaged so when they are damaged then that's it.
  4. Each hair responds to different frequencies and volumes. The hair cells send a signal to the brain and depending which combination of hairs are sending off signals your brain interprets it as a specific sound.
  5. Too much noise physically stresses and breaks these hairs meaning they no longer hear that sound.

That's enough to get an idea of how you hear something.

Hearing different sounds

The ear does not hear all sounds at the same volume and in effect amplifies the areas which are most important in speech which means we are basically tuned to hear speech over and above other noises. This is great as it means we can communicate even when there is a lot of background noise. 

The problem is that the ear is always amplifying the frequencies most important to speech, so when the background noise (such as industrial machinery or music) also includes these frequencies at a very high volume, the ears are still amplify the bits which are most sensitive to speech to make those parts even louder and we end up with these specific most sensitive frequencies being the first to get damaged and becoming less effective.

As a side note, ears can take a bit of excess noise, hence the averaging of the limits over time at work. With employees I always take the approach of describing it that they have a chunk of loud noise that they can have and that their ears can take, so what would they rather that allowance be used on, music or a restaurant or the cinema or a night out, or on the sound of a punch press or a compressed air vent or a packaging machine.

The effect on how we listen and life

This means that too much noise takes specifically speech out first. It's worth highlighting that at the beginning stages you don't really hear overall volumes any lower so things don't sound quieter and the sufferer will not usually notice any reduction in volume. What does happen is that speech starts to sink into the background noise, become less clear and gets merged into it .

Check out the Hearing Loss Demo pages for an example of what this effect sounds like via filters applies to a piece of music.

At first the person will probably start to notice it maybe at work, but also in places like really busy pubs or restaurants. People may sound like they are mumbling or not speaking loudly or clearly. They find themselves asking people to repeat what they said more often.

As it progresses they often start to avoid these kind of social situations as they feel like the grinning idiot in the corner. Everyone is chatting away and they can hear the music clearly but can't really make out what people are saying at all. It's worth highlighting that in a hearing test, for a middle aged person this probably would still count as a 'pass' even though they effects are quite noticeable in their daily lives.

Family life suffers as they cannot hear people talking over things like the TV or music playing. 

With continued exposures things like the TV become hard to follow, especially when there is background music behind speech which is the case on most dramas. All the sufferer hears is a mushy mess of noise with really indistinct speech. So they turn the volume up. Now the neighbours three doors away know what they are watching on telly but to the sufferer it doesn't help much, it's just a louder mushy noise. Most people they know will point and laugh and take the piss and tell them they are an deaf old fart as even though they are in their early 40s they are clearly getting old, but this loss is entirely preventable and is not an inevitable part of knocking on a bit.

They generally become more isolated from social situations at this point and overall hearing volume starts to go down as well. Eventually hearing aids are beckoning. There is no regrowing of those damaged hair cells or corrective surgery.

This is a radio interview with the great Murray Walker about his own noise induced hearing loss and the impact it had on him.

Tinnitus

What we haven't mentioned here is tinnitus. (Or as it was once memorably mis-stated to me, Tintinitus which sounds more like a fear of Belgian cartoon characters). This is the ringing, whistling, buzzing or otherwise sounds in the ear. They are there constantly and can also be caused by too much noise and the damage to those tiny hair cells. 

Tinnitus cannot be overlooked in how serious it is and it is thought to be a contributory factor to several suicides in the UK every year. To the sufferer the noises can be just as loud as real external sounds and at night when everything is quiet can sound especially bad, disrupting sleep and constantly screeching away. Imagine trying to sleep with this screeching away in your ears:

In May 2017, a Coroner's Inquest into the death of Inspiral Carpets drummer Craig Gill heard that he had suffered very badly from tinnitus in the weeks immediately preceding his tragic suicide. Tinnitus can be as life-changing as the loss in hearing, more so in severe cases. 

Summary

So this is why individual employees should give a damn about it. With regular exposures 'risk' is almost the wrong word and damage is a certainty, with the only question being 'how much'. The sufferer is usually not aware of the changes until they become severe, and there is no going back, no healing, no recovery. It impacts all areas of their life from social activities to watching TV or listening to music.

All this can be avoided by the humble hearing protector, either plug or muff.