THE TRUTH ABOUT NOISE INDUCED HEARING LOSS We hear from Stephen Wheatley of HearAngel, a new smartphone app designed to reduce hearing damage caused by headphones...
here’s a big, unspoken thing going on in the audio world. We all know it’s there, we all know how it happens, we all worry about it, and we all worry that if we start to suffer from its effects, then we won’t be able to do our jobs anymore. I’m talking about hearing damage – Noise Induced Hearing Loss (NIHL). When you hear sounds, you receive sound wave energy which ultimately vibrates hair cells in your inner ear. These hair cells convert the sound energy into electrical energy which travels to your brain. The problem is that when these hair cells are exposed to large sound doses, prolonged periods of sound, or short bursts of extremely high sound, they can become damaged and, once damaged, they are irreparable. To add to the problem, the effects are cumulative, and you are unlikely to realise that your hearing has been damaged until many years after exposure. One of the more common symptoms of NIHL is tinnitus, described as a continual ringing (or rumbling, crickets, sirens, whooshing noise, pulsing, ocean waves, buzzing, clicking – sometimes in combinations) in the ears. Ultimately, NIHL sufferers will also experience severe loss of hearing at mid to high frequencies (3 - 6kHz) which can make everyday conversation almost impossible. We all consider ourselves to be indestructible as teenagers – remember those nights in the pub, three hours sleep and a hangover? Each gig had its effects and they all accumulate over time, as we now know. Many people take better care of themselves as they
get older, but those in the audio industry have to carry on working for long periods exposed to high sound energy levels. If we worked in a factory, health and safety rules would force us to wear hearing protection, but that isn’t about to happen with PA sound, or broadcast soundies wearing comms headsets all day. Here’s how it works: According to the HSE, you are allowed to experience an average sound level of 85dB over eight hours or 40 hours in a week (although they have expressed the intention to revise this downwards soon). This means that the level can be louder than that sometimes, provided it’s quieter at other times, while sleep, rest breaks and meal times contribute to lowering this average level. The average level is also dependent on the type of audio you are listening to. For a given peak to peak level, speech has a low average level because of the pauses for breath and thought. Classical music has a higher average level as there are more sustained tones. With rock or dance music, the average level is much closer to the peak level – we all use compression to get the energy up in the room (and so also in our ears). The sound dose is also dependent on the amount of time we are exposed. In fact, it’s a direct relationship; if you double the level you are exposed to you halve the time of exposure. 85dB for eight hours, 88dB for four hours etc. The solution sounds obvious – reduce the dose. This means either reduce the level – tricky, (especially if you have a drummer) or reduce the exposure time – more tricky (especially if you give the drummer a solo). For acoustic exposure, the simplest and most affordable
way is the use of hearing attenuators. These are custommoulded earplugs that have a diaphragm which attenuates all frequencies fairly evenly, acting like a pair of sunglasses for the ears. They are very different from ordinary foam or wax earplugs, which will make the sound very muffled and hard to hear (much like the NIHL we’re trying to stop!). Attenuators work really well, although they will take some getting used to, as things do sound different when your ears are not being overloaded – persevere and you’ll realise that the reason they sound different is that you can hear everything much better. For reproduced sound exposure, you should choose headphones that isolate you from ambient noise, so you don’t have to turn up the level just to overcome the ambient. The problem with headphones is knowing just how loud you are listening, but there are some technologies that can help. If the headphones are shared, obtain headphones fitted with a fixed level limiter, such as LimitEar FL, which will ensure you don’t go over a pre-set level. If you have your own personal headphones, then there are dose management devices that will ensure that your entire daily reproduced sound dose is safe. LimitEars’ HDM Pro device ensures the daily reproduced sound dose is within HSE guidelines. If you are using a smartphone for listening, then HearAngel is an app that will monitor and control your daily sound dose. So, don’t stop listening to your favourite music or podcasts – just ensure you’ll be safe and protect your hearing while listening. n
Stephen Wheatley has spent six years creating occupational hearing protection solutions and is one of the founders of HearAngel – a smartphone app that helps users protect their ears from damage while using headphones. www.hearangel.com
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