[dhjdhj (OP)]

Given that people that work in noisy environments wear ear defenders, do hearing aids which amplify very considerably, actually cause further damage to already damaged ear follicles. No audiologists warn about this. Is there any research?

[evan_au]

I have heard that people whose hearing has slowly declined over many years get a painful audio shock when the audiologist sets their hearing aids to the "right" levels.

When they go normal places, the sound is abnormally loud, and it is hard to pick out voices amongst the noise. This causes some people to stop using them.

do hearing aids which amplify very considerably, actually cause further damage to already damaged ear follicles?

Hearing loss tends to be worst at high frequencies. Since the shorter hairs in the cochlea resonate at higher frequencies, it is the shortest hairs that get damaged first.

In the unlikely event that your hearing was unaffected up to (say) 1kHz, and declined above that, in theory the audiologist would not need to apply any amplification up to 1 kHz, but increasing amplification above that.

So there should be no additional damage to the longer hairs below 1kHz, but more signal power will be going into the (already damaged) short hairs.

Modern hearing aids also incorporate automatic gain control, so that if you walk into a really noisy room, it should back off the gain so it doesn't generate really loud signals into your ear.

[chris]

This is a really good question. Thanks for asking it. In fact, I've wondered about it myself for years. I suspect that the answer is that that the energy being applied to the ear is likely to cause further decline in function, albeit restricted to the amplified frequencies (as alluded to by Evan above), but if a person is already struggling sufficiently so as to need a hearing aid, and their quality of life is already suffering as a result, then it is hard to argue that they are worse off as a result.

Meanwhile, we made a programme about the science of hearing and the science of hearing aids; it's quite a good listen (if you'll excuse the pun!) and might be helpful for you:

http://www.thenakedscientists.com/HTML/podcasts/show/20121014/

[dhjdhj (OP)]

My own suspicion is that this is the case. My wife is very hard of hearing and has had progressively more powerful HAs until now she has such severe loss that she is going through assessment for a cochlear implant. During this process of repeated hearing aid fitting, new aids always need adjustment upwards after being fitted for a week or two and I suggest that is because the additional energy damages more follicles. There is research in California that uses lasers to bypass the ear drum and directly excite the cochlear creating electrical impulses without using the follicles, so being entirely non invasive and non amplifying. Does any one out there know more about this?

[chris]

I think this is a proposed optogenetic technique whereby cochlea cells are made light-sensitive through expression of an exogenous gene; the laser illuminates discrete populations of these cells corresponding to the input sound frequencies. The light stimulus, detected by the light sensor on the cells, is linked to ion channels that can trigger action potentials as though the cells were responding to sound.

I was aware that people were trying this in animals; I am not aware of this being done in humans - if you have details of a human clinical trial that you can send me, or I am barking up the wrong tree, please let me know.

[dhjdhj (OP)]

I don't know of any trials, but Lockheed Martin Aculight has a contract I believe supported by DARPA. Information is sketchy and I have no way of pursuing it (despite working with Lockheed in the 1990s). There is an article in Popular science www.popsci.com/technology/article/2012/04/how-it-works-artificial-hearing-device . If you can find out more I am sure I am not the only one interested. It might make a great podcast.

[Edmonn]

It’s true that your eardrums can get damaged if powerful sounds are played directly next to your eardrums. However, if you have hearing loss, the volume of well-fit hearing aids won't be loud enough to do harm. An accurate and appropriate hearing aid programming is what makes a hearing aid fitting successful. Look for the latest hearing aid technologies in (MOD EDIT: Commercial link removed). Hearing aids are not only safe, they're life changing too. The latest research by the university of Texas shows that hearing aids improve brain function in persons with hearing loss without affecting the ear.

[BrotherJ]

When a hearing aid is appropriately fit, programmed, verified, and validated, there should not be any concerns of hearing loss caused by hearing aid use. Documenting a real-ear verification measure where the maximum power output (MPO) is measured and adjusted if necessary is critical.  This is one reason among many that working with a trained professional who always utilizes real-ear verification including MPO is so important.  The risks of untreated hearing loss by not using hearing aids are well-documented and far greater than the low likelihood of concerns of hearing damage due to over amplification.

[aentscthartford]

Hi… there are many people who think this after wear the hearing aids and also ask, they hear without their devices because the sound plays next to the eardrum. So, there is the possibility of further hearing loss. For proper diagnosis you should be consult with ENT Specialist doctors.