What REALLY are hearing aids?

apparent loudness is a complex function of frequency, the human ear has a peak of sensitivity at a couple kHz, for someone with normal hearing a sine wave in that range at a certain SPL will be painfully loud and then at 50Hz same SPL won't even be able to hear it.

Hearing loss affects different frequency ranges by different amounts, too. Hearing loss manifests differently in different environments like say watching TV in a quiet home vs. trying to hear a conversation in a crowded restaurant or someone giving a presentation in a lecture hall.

for some time pure electronic amplification was all there was but it wasn't ideal for many kinds of hearing loss it's a sledgehammer approach.

Digital signal processing to change amplification profiles automatically with environment, tailor gain boost for individual frequency bands and a person's hearing loss profile, prevent feedback, do automatic gain control, etc. usually produces much better results.

Or rather, just dumb broadband electronic amplification

Amazon will sell you a pair of hearing aids for $21.

Hearing aids aren't just amplifiers. They change the tonal characteristic to compensate for the loss of hearing at certain frequencies, usually high frequencies. This is filtering.

That said, they are made using mass production and can be produced at rough ly the price of a bluetooth earpiece. So $50 each for a good model would n ot be overpriced. This would not include fitting or any adjustments requir ed at the time of purchase. This is a bit the opposite of glasses where mo st of the cost is making the glasses and minimal cost in fitting them.

Rick C.

Yeah but most people wouldn't appreciate the cosmetics of a bluetooth earpiece. Those hearing aids are TINY. This would not include fitting or any adjustments required at the time of purchase. This is a bit the opposite of glasses where most of the cost is making the glasses and minimal cost in fitting them.

It's a MEDICAL device. Tightly controlled supply, high demand. Somebody has to pay for the office and the staff and the doctor's boat and his malpractice insurance...most importantly, the boat.

We've come a long way. I remember back in the day when hearing aids were brick-sized boxes that hung from the wearer's neck, swinging back and forth with every movement. The one visible in this classic comedy clip is relatively small compared to the early aids:

You can get basic aids like that for under a tenner on amazon or ebay. They're ok for mild hearing loss. Modern ones are normally more complex. Some of what they do has been explained, they can also include high frequency downshifting.

NT

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tic to compensate for the loss of hearing at certain frequencies, usually h igh frequencies. This is filtering.

oughly the price of a bluetooth earpiece. So $50 each for a good model wou ld not be overpriced.

Not necessarily and many bluetooth devices are just as tiny and the ones wh ich fit in the ear canal.

My 92 year old friend has a pair of hearing aids that fit behind the ear wi th a tiny tube with an end that fits in the ear canal. It is very unobtrus ive and has room for a battery he can replace even though he is legally bli nd. They can be made to sell for about $50 each if it were just a matter o f unit pricing.

Something happened in the quotation. This is what I wrote.

Supply is not "tightly" controlled. There are plenty of companies making a nd selling them. Like with glasses, the doctor has nothing to do with the sale of the hearing aid. The doctor simply writes the prescription.

I think the fact that hearing aids require a prescription means people beco me shy about price shopping. They get "free initial visit" coupons in the mail and once in they are much more likely to buy. In Maryland if someone comes to your home to quote you a price on a new storm door they are not al lowed to accept payment that same day. They have to return for a second vi sit. Maybe we need to have something like that for glasses and hearing aid s. That would break the "free consult" momentum and give people more encou ragement to shop it around.

Rick C.

I had a virus or something a year or two ago and my ears were temporarily affected so I went to see a local (and new to me) Ear Nose and Throat specialist doctor along with a hearing test.

I asked the Dr. why they stopped the test at 8 kHz. He said it was because most people cannot hear much above that except for rarely few and children that might be able to hear up to maybe 10 kHz.

What the hell is the medical world coming to ?!?!?!?!!!?? I guess he had never been near a color CRT TV with 17.734 kHz horizontal nor had heard of the 20Hz to 20kHz typical hearing range before.

I suppose I must be special because even at 65 yrs old I can still hear up to almost 13 kHz.

Yes, hearing aids these days do have DSP in them and do a lot more than just amplify.

My father started with one of those, and later graduated to one the size of a matchbox mounted on his chest. BTE, ITE and IC aids never worked due to the extent of his deafness.

He did buy a "private" hearing aid once, but it was nowhere as good as the ones he didn't have to fork out lots of money for. Thereafter he relied on the ones that were issued FOC.

I just turned 79 and I can hear a little past 8khz. When I was 16 I could hear

I topped out at 11khz last time I checked (also using a HP sig-gen).

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"Hearing aids" are very expensive because they are classified as medical devices and are tightly regulated.

"Hearing assist devices" are not classified as medical devices and are much less expensive.

I'm 40, thru a pair of high-quality headphones I can just _maybe_ perceive 13kHz, haven't had it tested professionally recently I'd imagine they say I top out at 12.

My girlfriend is 34, not sure how high hers goes but she says she can hear my cell phone making clicking and high-pitched whines when it's connected to its charger brick that I definitely don't hear.

====snip====

That must have been painful.

It's about time someone open-sourced a DSP design, it's no longer rocket science, and I suspect there is a protected market with much markup....

... and sadly lawyers ready to sue, if someone's hearing got damaged due to incorrect application of an unapproved device.

The latter is *not* a remote possibility.

As I noted elsewhere, severe hearing loss allows the ear-brain to invent sounds to fill in the gap. That's tinnitus, which can be fatal since people will do /anything/ to escape the noises.

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Can't limiting the output to safe values avoid causing that problem?

Perhaps that might be doable with a passive RC on the output so that 4kHz o r thereabouts uses full output swing without giving the speaker enough to c ause a hazard, whereas at lower f the speaker can get much more V_out. Far safer than limiting output in software.

NT

I don't think the hardware is really the sticking point any more. Some of the algorithms are trade secrets though. The patents only tell a part of the story where someone thought they could lock the opposition out. eg.

It is the effort needed to adjust the thing to optimise intelligibility for the patient requiring careful and time consuming laboratory tests in a soundproof room that add to the cost.

The chipsets to do DSP on a very tight power budget are distinctly non-trivial and use various cunning tricks eg.

You pay through the nose for something DSP based that is in ear and invisible but the DSP ones that fit around the ear and acoustically couple are now relatively cheap - at least outside of the USA.

It is a lot easier if you don't have to microminaturise to fit inside the ear and can use a sensible size capacity battery.