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Threshold of hearing compensation

Started by Unknown May 5, 2019
There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). I’m no audiologist but this seems suspicious to me; I don’t think having a high threshold is the same as just turning down the gain at that frequency as if your ear were just a graphic equalizer.  But maybe I’m wrong.  Anybody have an opinion on this? This is probably the wrong group but I’m guessing there are people in the audio DSP world who would have some knowledge in this area.  

Bob
On 06/05/19 00:02, radams2000@gmail.com wrote:
> There are several new consumer headphone products on the market that allow > you to measure your threshold of hearing using an app on your phone and then > auto-adjust an equalizer to boost the areas where your threshold is high > (indicating hearing loss at those frequencies). I’m no audiologist but this > seems suspicious to me; I don’t think having a high threshold is the same as > just turning down the gain at that frequency as if your ear were just a > graphic equalizer. But maybe I’m wrong. Anybody have an opinion on this? > This is probably the wrong group but I’m guessing there are people in the > audio DSP world who would have some knowledge in this area. > > Bob >
I've just written this on a different NG in response to a different question. Nonetheless, it indicates why you need an audiologist, not a DSP expert...... The ear-brain is highly non-linear in ways that I only dimly comprehend. Consult textbooks and the literature for more information. Start by understanding that the nominal frequency response is dependent on the amplitude. Base/treble controls change the frequency response in the same way whatever the amplitude. Clearly that doesn't match the way the ear-brain perceives sound; in effect the "ideal" bass/treble control setting at one amplitude won't be the ideal setting at louder/softer amplitudes. A "loudness control" is an attempt to have a base/treble boost/cut that changes with the amplitude, that matches how sound is perceived. Now imagine having a different loudness control for each deaf person, because each deaf person's impairment is unique. What does that mean in practice? I recently had two new hearing aids, where the process was: - 45 mins quickly assessing my hearing, so as to determine which type of aid is appropriate, plus taking ear canal moulds for two new earpieces - after the moulds had been manufactured, a 1.75 hour session that: - accurately measured my hearing loss in each ear, air and bone conduction, plus a masking test to ensure my right ear wasn't hearing sounds played into my left ear - discussing what I wanted the aids to achieve, in order to set appropriate programmes - tweaking each *aid's* frequency response to be the inverse of my hearing response, plys setting appropriate companding and limits - with the aids in my ears, measuring the effect ` the ear *canal* has, and re-tweaking each aid to get the desired response, companding and limits I will have another appointment in a few weeks to re-assess what has worked, hasn't worked, and re-tweak everything. So, not cheap, not easy, and there is a high degree of sophisticated assessment, measurement, and tweaking involved. It sure the hell isn't a simple amplifier and tone control! Now not everybody will have hearing as bad as mine, but the processes listed above will be pretty similar for everybody.
Thanks Tom.  I should have mentioned that these products are actually meant for music playback. The theory is that you can customize the EQ based on hearing threshold measurements. 
On Monday, May 6, 2019 at 12:23:14 PM UTC+12, radam...@gmail.com wrote:
> Thanks Tom. I should have mentioned that these products are actually meant for music playback. The theory is that you can customize the EQ based on hearing threshold measurements.
don't see why not, but the human ear has an average threshold of hearing curve based on age. Unless you are hearing impaired there is no need to play around with this. Certainly don't want to equalise them and make them flat since you may not find that pleasing. I suppose you could boost certain frequencies to bring them back to the ideal curve but that is what a hearing aid does anyway.
On 5/5/19 4:02 PM, radams2000@gmail.com wrote:
> There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). I’m no audiologist but this seems suspicious to me; I don’t think having a high threshold is the same as just turning down the gain at that frequency as if your ear were just a graphic equalizer. But maybe I’m wrong. Anybody have an opinion on this? This is probably the wrong group but I’m guessing there are people in the audio DSP world who would have some knowledge in this area. >
hay Bob, i would think of it as a sorta first order approximation. i would expect that the EQ would boost the bands where your ostensible threshold is higher than the 0 dB Fletcher-Munson value at that frequency. i dunno what other basis to go by. around 2008 i found out that i lost 30 dB at ca. 4 kHz but i still want my music EQed flat. i certainly do not want it boosted 30 dB at 4 kHz. workin' for JJ at the Left Coast. if you want, lemme know if you might end up visiting Seattle. L8r, -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Am 06.05.19 um 01:02 schrieb radams2000@gmail.com:
> There are several new consumer headphone products on the market that allow you to measure your threshold of hearing using an app on your phone and then auto-adjust an equalizer to boost the areas where your threshold is high (indicating hearing loss at those frequencies). I’m no audiologist but this seems suspicious to me; I don’t think having a high threshold is the same as just turning down the gain at that frequency as if your ear were just a graphic equalizer. But maybe I’m wrong.
You are not wrong. Doing so is crap. Aurally handicapped people would tell that it is absolutely useless to just raise the level of frequencies where you are handicapped. Quite the contrary. Doing so may prevent you from hearing /important/ parts of the signal. Furthermore loudness is nonlinear. The threshold level is not representative for the frequency response at reasonable sound levels at all. The result would be just the loudness correction - some of us may remember this sin of the 80's.
> Anybody have an opinion on this? This is probably the wrong group but I’m guessing there are people in the audio DSP world who would have some knowledge in this area.
Well, it is possible to improve hearing using a DSP. Hearing aids made great improvements over the last years. But the processing is by far more complex than a linear transformation. Multi band compression, adaptive filtering and other non-linear operations are essential. Basically taking away insignificant parts of the signal to bring out important parts more clearly. I am no expert in hearing aids. But I have some experience with DSP sound processing. E.g. I use digital room correction for more than a decade (with homebrew software). But my goal was never to adapt my acuesthesia but only to compensate for insufficiency of the sound reproduction system. There is no much absolute in hearing at all. We just identify sounds that we have listened before. The more different the signal you feed to your ears, compared to your personal experiences, the worse the recognition of it. So let us just call it a marketing gag. Marcel