What causes hearing loss?

03 April 2018

Interview with

Bella Bathurst, Author of 'Sound', & Professor Brian Moore, University of Cambridge

What causes hearing loss and what is it like? Georgia Mills heard from Bella Bathurst, author of the book 'Sound', and Professor Brian Moore of Cambridge University.

Brian - There are many causes of hearing loss. There’s likely to be a genetic component, so different people vary in their susceptibility to getting hearing loss. And there are quite a large number of genes now have been identified that affect hearing and, if you have a problem in those genes, you’re almost bound to get the hearing loss.

But there’s also strong evidence that noise can damage hearing, so intense sounds generally, which used to be used produced mainly by factory noise. Now even leisure noise, very loud concerts and discos can damage your hearing, or working in the military can be very dangerous as well and many people are still being deafened by working in the military.

There are also many drugs that can affect hearing: antibiotics ending in “mycin”; kanamycin and neomycin will poison the ear if they’re given in large enough doses. And many drugs used to treat cancer, particularly ones with platinum in them can damage these hair cells in the inner ear.

Georgia - Now I’m just worried about being an audio producer. It’s probably not a great experience for my ears. Do we know why loud noise has this affect, and could it be one very very loud bang or is it over time?

Brian - Again, there are probably different mechanisms. If you have an exposure to a brief, really intense sound like a gunshot or an explosion, that can actually produce structural damage inside the cochlear; it basically is ripping up the structures, which is very nasty. But for more moderate, long term exposures like working in a noisy factory or going to a loud rock concert, there seem to be metabolic processes that take place in the cochlear that can actually poison the structures inside the cochlear. It’s a bit like if a marathon runner overdoes it, all the metabolites that build up in their muscles can poison the muscles. And this active mechanism that I talked about requires quite a high metabolic turnover, and if you work it really hard because of intense sounds coming in, the chemicals that build up in the cochlear can result in the hair cells being poisoned and then they die off and, unfortunately, once they die they never come back.

Georgia - So it’s like if I were to run well, judging by me about five minutes and I would get a stitch, it’s like the audio equivalent of a stitch and the bad chemicals just build up?

Brain - That’s right. And, of course, in our muscles we have receptors that tell us when things are going wrong; it starts hurt and become painful and then you stop doing it. But it’s not clear yet whether the ear actually has pain receptors and so we may do all this damage to our ears without actually feeling anything bad going on, so that’s a real problem I think

Georgia - So please do adjust your sets and turn down the volume. But it is being predicted that with our current music behaviours, hearing loss is going to continue to rise.

Bella - People are always being told to turn down their ipods or whatever it is but, actually, there is a bit of an epidemic of hearing loss coming for the young as well. You can completely see why because most music, or a lot of rock music, is not supposed to be heard quietly, it’s designed to be loud. With all that I know about hearing, I still want to stand next to the amps because that’s the only way that you get that thud in your heart, in your bones.

Georgia - Bella Bathurst is the author of the book “Sound.” She knows exactly what it is like to go deaf, as when she turned 27 she started to lose 50% of her hearing.

Bella - Signs that had previously been audible like station announcements, or people’s voices, or laughter, or whatever it was just became inaudible. The sound of a mobile in another room had previously been easy to hear and then it became difficult to hear, so it was a sort of gradual muffling. But one of the odd things about hearing loss is that it makes your more aware of acoustics and your sound environment, not less.

Georgia - What do you mean by that?

Bella - I just became completely obsessed with rooms and spaces. There are certain situations which are much more difficult, it doesn’t matter what kind of of hearing aids you’ve got and what kind of amplification. Outside, where sound is very echoey and it gets blown away very easily, it’s much more difficult than a nice, muffled, low ceilinged room with lots of carpet and lots of fabrics.

Georgia - The kind of rooms I look to record in?

Bella - Absolutely. I was looking at the studio here and thinking ideal acoustic environment.

Georgia - With this time when you lost 50% of your hearing, did that stay consistent?

Bella - No, it kept on dropping. By about 2009, which is when I was re-diagnosed, it was down to about 30% in both ears, probably slightly worse in the left ear.

Georgia - How did that change your life?

Bella - I’ve always been a writer, and the bit of the job that I always enjoyed most is interviewing, and I worried most of all that it was making me unprofessional because when I played back those interviews, I would hear how many times I hadn’t heard, or had misheard, or come out with a completely wrong connection or something and I really hated that. I thought that was terrible and so I felt very guilty and rather ashamed, and I also felt horrified at the idea that I might be blanking people without meaning to.

I also resented actually, going deaf aged 27. I disliked the stigma that deafness has that it’s to do with age and I’m afraid to say stupidity. People see deafness as something that’s connected to slowness and I’ve fought those things quite hard. And now, I’ve just got exhausted and then I just got depressed, which I think is common to a lot of people with hearing loss that what it wants to do, what deafness wants to do, is to push you away from your fellow human beings and into a state of isolation.

One of the things that I realised when I started researching the book, which I found completely fascinating, was that without prompting, without me looking for it, every single person who I spoke to who had hearing loss said: I find it completely exhausting. I sleep like I’ve been clubbed. I need 10 hours of sleep a night or whatever. People do find it completely knackering and again, people tend to sort of blame themselves for finding it knackering.

Georgia - Hearing aids are usually the first port of call for someone who is losing their hearing. These essentially turn up the volume by receiving sounds through a microphone, boosting the volume electronically before rebroadcasting sounds into the ear through a tiny speaker. They can make a big difference, but in some situations, like outside or in an busy room, or for some types of deafness, they aren’t very effective. But there’s lots of work into improving them. Here’s Brian again…

Brian - One thing that people are working on that’s still in the future is that you would actually pick up electrical signals from the person’s brain to decide who they were trying to listen to, and then you would steer the beam in that direction. But that’s still some way ahead, but there is a large research group working on that right now.

Georgia - That's incredible! So really smart hearing aids - you can decide you’re finding this person really boring, just shut them off and turn up the other...?

Brian - Exactly, yes. What we do have already are hearing aids that you can control from smartphones, and you can use the smartphone to control the operation of the hearing aid to some extent and set it up in different situations. But the smartphones can also do what’s called geotagging, where they remember how you set up the hearing aid in a specific situation and when you next go back to that same place it says “oh, this is the same location as before” and it automatically sets up the hearing aid the right settings for that situation.

Georgia - That’s incredible! So I guess compared to my glasses that are just pieces of glass, they have to be very active and clever machines?

Brian - Yes. Nowadays, hearing aids are miniature computers and they pack a lot of computing power into a very small space, all operating of 1.1 volts.

Georgia - Wow! Because I know when I’m editing sound and changing the pitches my software takes about five minutes to do it, it has to do it all in real time?

Brian - Yes. This has to all be done in real time. And it’s got so complicated that I think, even within one manufacturer of hearing aids, there’s no single person who understands how everything in the hearing aid works. Each person does one block in the processing and then somebody tries to put it all together, but it requires a big team to get all these things working in a coordinated way.

Georgia - Ah! So optometrists have it easy?

Brian - Yes, the do indeed, yeah.


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