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ANDY COULES: Your Ears - A User Manual

ANDY COULES: Your Ears - A User Manual
Andy Coules

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02 October 2013: By Andy Coules

Why regular hearing maintenance is essential, and how to ensure that your ears are properly looked after.

Why regular hearing maintenance is essential, and how to ensure that your ears are properly looked after.

Your ears are arguably the most important tool at your disposal yet they are rarely maintained, frequently abused and often ignored. They're incredibly sensitive yet extremely resilient, and capable of capturing everything from the distant buzz of an insect to the full throated roar of a rock band and beyond. Yet when they break that's it, they can't be replaced. So lets take a look at how they work, what can go wrong and what we can do to ensure a long working life.

Sound vibrations are collected by the external pinna, which filters and reflects the sound into the ear canal – a slightly curved tube about two to three centimetres long at the end of which is the ear drum. The ear drum is connected to three tiny bones called ossicles, which mechanically transfer the vibrations to the inner ear, and in so doing can amplify the vibrations by a factor of 20. The inner ear contains the Cochlea, which is liquid-filled and contains a membrane lined with hairs that vibrate in response to different frequencies generating nerve impulses for interpretation by the brain.

The moving parts of the ears are subject to wear and tear just like the rest of the body, thus your hearing deteriorates naturally as you get older (the peak age for hearing acuity is 18). Various other factors can affect your ears' ability to function, including physical trauma, illness, medication and noise.

The ear drum is a thin flexible membrane, it's no accident that it's safely tucked away inside the head as it's quite easily damaged. Perforation can occur as a result of infection, explosion / loud noise or from being punctured. This causes conductive hearing loss (i.e. a break down in the ear's ability to conduct vibrations), which is quite unpleasant, but usually temporary and rarely has a long term impact on the hearing.

Therefore, one thing you should never ever do is clean your ears with cotton buds. Your ear has an in-built cleaning system involving the production of a yellow waxy substance called cerumen, which attaches to dirt / grit and then politely escorts it off the premises, so is best left alone. Cerumen can also build up around the ear drum and impede it's movement, resulting in muffled hearing. Regular use of ear plugs or in-ear monitors can exacerbate this issue, but wax build up is easily dealt with using ear drops or in extreme circumstances syringing – a quite pleasant process involving having warm water pumped into your ears.

There are various infections that can affect the outer and inner ear, which are usually treated with ear drops or antibiotics, always seek medical advice promptly to avoid unnecessary down time. Common colds also have an impact as a build up of mucus or an inflammation of the sinuses can block the eustachian tube. The eustachian tube links the middle ear to the back of the throat and opens when you swallow to equalise the air pressure behind the ear drum. When blocked it can cause the ear drum to stretch and distort resulting in muffled hearing (anyone who's flown should be familiar with this sensation).

By far the biggest risk is noise induced hearing loss (NIHL). This is where excessive and persistent noise damages the physical mechanism of the ear. The most common area for damage is the frequency sensitive hairs in the cochlea. The ones that vibrate in response to mid/high frequencies are more delicate and thus more easily damaged. Once damaged these hairs do not grow back.

Thankfully your ears have a couple of in-built safety features for your protection. The narrowing of the ear canal physically limits the amount of air which can pass through to the ear drum, thus acting as a kind of input compressor. There are also muscles in the middle ear, which can tense reflexively in reaction to loud sounds, and prevent the ossicles from amplifying. Be aware that the use of ear buds or in-ear monitors (i.e. physically placing a speaker inside the ear canal) can bypass these protection mechanisms.

In order to avoid NIHL it is important to be aware of the risk at all times (not just at work) and limit your exposure accordingly – the risk of damage increases not just with level but also with time. I like to use the rough guideline that you can tolerate 94dB SPL for one hour before damage is likely and that for each doubling of the level (i.e. +3dB) the time is halved (so you can tolerate 97dB for 30 minutes, 100dB for 15, etc.). If you don't know what 94dB sounds like you can get inexpensive key ring noise level indicators or apps, although be aware that an app may need to be calibrated with a decibel meter in order to be accurate.

A good way to limit your exposure time and protect your hearing is to wear ear plugs. Various different types are available – the three most common are custom moulded, non custom and generic foam, which either provide a fixed level of attenuation or enable interchangeable filters. The level of attenuation is not equal at all frequencies so the more attenuation there is, the less accurate the frequency response tends to be. As a general rule the more expensive the ear plugs the flatter the frequency response.

Therefore I use different plugs depending on the level of protection required and how accurately I need to hear what's going on. For the most critical listening applications (e.g. FOH mixing) I'll start unprotected, get the mix sorted and then pop in -15dB plugs/filters to finish the set; if the set is longer than an hour I'll use -20dB plugs/filters. When the set is finished and the DJ kicks in I'll switch to -30dB foam plugs so I can move around the PA/stage comfortably. I always carry ear plugs with me and use them whenever the sound levels get excessive (at gigs, night clubs, etc.) – you may be off duty but your ears never are.

Just like any equipment you should schedule annual maintenance reviews (i.e. ear tests) and if you suspect a problem get it checked out by a professional. Regular rinsing with salt water will aid the natural cleaning process and a drop of olive oil will help soften the wax and prevent build ups. With a little bit of awareness and some care you can ensure a long and productive working life for you and your ears.

Andy Coules (andycoules.co.uk) is a sound engineer and audio educator who has toured the world with a diverse array of acts in a wide range of genres.