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Audio: How We Hear

amirm

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#1
Our resident technical and psychoacoustic expert and research/industry luminary, @j_j, recently gave a talk at our local chapter of Audio Engineering Society. He calls it Hearing 099. I tried to make it more descriptive and hence what is in the title. It is not very accurate but hopefully it is enough to get your attention. :)

I should tell you in advance that JJ's talk is a mix of very simple and useful information -- some summarized in just one sentence -- and others which will be complex and probably hard to understand for most of you. The simple messages are spread throughout the presentation so please set aside an hour and listen to it. And don't skip the last 5 minutes, whatever you do.


The talk will be the start of your understanding of our hearing system and likely something you will come back to often. It will also be a jumping point to learn more using other online resources. It is the best presentation I have seen as the topic is often described at too high level, or way too low.

Hopefully JJ will be available to answer questions as he did from the audience.
 

anmpr1

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#2
Anecdotally, I've found that my hearing acuity fluctuates depending upon (as far as I can tell) atmospheric pressure. Sometimes things are very clear, and other times muffled. I correlate it with the weather. Obviously the 'what' of the hearing has not changed. It's most likely an inner ear thing. On another note, I've been going over some ABX analysis, and some studies report that in upwards of a third of the cases, people report hearing 'differences' when the same component is compared with itself.
 

RayDunzl

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#3
Anecdotally, I've found that my hearing acuity fluctuates depending upon (as far as I can tell) atmospheric pressure. Sometimes things are very clear, and other times muffled. I correlate it with the weather.
I notice the same occasionally. I'll agree with air pressure difference on the "eardrum".

Carefully adding (equalizing) pressure on the inside makes things right again. It creeps up on me, don't know the physics of the pressure differential. Maybe gas in the inner ear is slowly absorbed into the tissues, and if the eustacean tube is stuffy, you have to gently force equalization.

Maybe it is a barometric pressure change (and stuffy eustachian). I'll note the mercury barometer next time I feel it happen to me. 29.9 inches right now, hearing feels normal to me at the moment.
 

rmo

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#4
Anecdotally, I've found that my hearing acuity fluctuates depending upon (as far as I can tell) atmospheric pressure. Sometimes things are very clear, and other times muffled. I correlate it with the weather. Obviously the 'what' of the hearing has not changed. It's most likely an inner ear thing. On another note, I've been going over some ABX analysis, and some studies report that in upwards of a third of the cases, people report hearing 'differences' when the same component is compared with itself.
Atmospheric pressure and humidity levels as well . Nicely said and very true
 

Sal1950

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#5
Carefully adding (equalizing) pressure on the inside makes things right again. It creeps up on me, don't know the physics of the pressure differential. Maybe gas in the inner ear is slowly absorbed into the tissues, and if the eustacean tube is stuffy, you have to gently force equalization.
You have to inhale deeply, hold it as long as possible, then exhale slowly.
Works to eq inner ear pressure just right. ;)
 

Blumlein 88

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#7
Very nice talk. Glad this was put up. Plenty of interesting points scattered through out. I hope there are parts 2 and 3.
 
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Jimster480

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#8
I've been meaning to set aside an hour to watch this. Just haven't been able to yet.
It looks very interesting. I'm sure as @amirm said that some of it will go over my head... but that is fine. I'm always trying to learn new things.
 
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#9
Highly recommended. Lots of good information, and some of the most interesting stuff comes in short sentences in between.

But it does not come easy, a solid technical background makes it possible to get more out of it. I watched it 2 times, and occasionally paused the video, to think over.

More focus on how hearing works and less on optimization of non-existing problems has been the key for getting results that matter, for me. This is where the progress will be in future audio.
 
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#10
I notice the same occasionally. I'll agree with air pressure difference on the "eardrum".

Carefully adding (equalizing) pressure on the inside makes things right again. It creeps up on me, don't know the physics of the pressure differential. Maybe gas in the inner ear is slowly absorbed into the tissues, and if the eustacean tube is stuffy, you have to gently force equalization.

Maybe it is a barometric pressure change (and stuffy eustachian). I'll note the mercury barometer next time I feel it happen to me. 29.9 inches right now, hearing feels normal to me at the moment.
Yeah, holding my nose with 2 fingers, mouth shut, then blowing hard until teardrops appear (...sometimes, when there is not too much pollen in the air...) improves a lot my hearing quality. Afterwards opening the mouth as far as possible, equalises the overpressure, but maintains at least 6dB better sensivity and high frequency response.
Of course this may be a very personal effect (...me, in the late 50´s...still able hearing up to 15KHz), but doing it repeatedly before and while listening at decent levels is a real benefaction to me.
--- If you should consider repeating this by yourself, please take care of the felt limits of your own physiology! ---
Anyway, my personal explanation for this effect is a temporary reduced thixotropy in my tympanic membrane, the oval window and/or the joints between the auditory ossicles...caused by pressure stretching through the eustachian tube...
 
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j_j

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#11
Anyway, my personal explanation for this effect is a temporary reduced thixotropy in my tympanic membrane, the oval window and/or the joints between the auditory ossicles...caused by pressure stretching through the eustachian tube...
What you're doing is equalizing the pressure on both sides of the eardrum, reducing the tension, and changing the middle ear response quite a bit.
 

senmurv

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#14
Brilliant! Of course every person is going to have his or her own head transfer function ... unless you have an identical twin ;) ?
 
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#15
What you're doing is equalizing the pressure on both sides of the eardrum, reducing the tension, and changing the middle ear response quite a bit.
That´s probably the case, the frequency transfer function of the middle ear changes (in my perception to the better), but the effect takes place only if you "blow up" the middle ear through the eustachian tube before and then release the overpressure completetly by max. mouth opening (or like someone trying to normalise falling cabin pressure in an ascending plane).

There are more interesting (self-observed) effects of the aging ear, like susceptibility to doppler-caused IMD (vibrating loudspeaker enclosures) or perceived distortion from short-path wall echoes (<2m)...in case of interest I could describe them at a later point in time...
 

j_j

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#16
Brilliant! Of course every person is going to have his or her own head transfer function ... unless you have an identical twin ;) ?
That's still not likely to help, unless you have the same haircut, same shirt, ...

The good news is that you can adapt to a generic one if it's close enough to begin to understand.
 
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#17
Brilliant! Of course every person is going to have his or her own head transfer function ... unless you have an identical twin ;) ?
I think the middle ear transfer function is part of ones HRTF (according to English Wikipedia, German Wikipedia does not state it that clearly...). Anyway everybody is used to his or her individual HRTF and what I am writing about is a temporary change of my HRTF.
 

senmurv

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#18
@j_j @eliash I was being funny with my identical twin comment. Transfer functions are all about estimating a dynamic model and as @j_j said every little nuisance will affect the model .... you can only hope to get close and that often is good enough :D ... Just joined this forum and loving it!
 
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#19
That´s probably the case, the frequency transfer function of the middle ear changes (in my perception to the better), but the effect takes place only if you "blow up" the middle ear through the eustachian tube before and then release the overpressure completetly by max. mouth opening (or like someone trying to normalise falling cabin pressure in an ascending plane).

There are more interesting (self-observed) effects of the aging ear, like susceptibility to doppler-caused IMD (vibrating loudspeaker enclosures) or perceived distortion from short-path wall echoes (<2m)...in case of interest I could describe them at a later point in time...
Need to correct my above statement a bit by definition according to english Wikipedia, it says:

"A pair of HRTFs for two ears can be used to synthesize a binaural sound that seems to come from a particular point in space. It is a transfer function, describing how a sound from a specific point will arrive at the ear (generally at the outer end of the auditory canal). "

So it looks like the middle ear transfer function is not part of the HRTF...
 
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j_j

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#20
I think the middle ear transfer function is part of ones HRTF (according to English Wikipedia, German Wikipedia does not state it that clearly...). Anyway everybody is used to his or her individual HRTF and what I am writing about is a temporary change of my HRTF.
HRTF ends at the eardrum. When we're talking headphones, vs speakers, it ends at the entrance to the ear canal, because you're already used to your ear canal resonances.
 

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