ear buzz update

[John Ross]

Thank you, Sarah.
Definitely an answer more involved, than I expected.
Nice to have you back on the list.
John
John M. Ross
Windsor, Nova Scotia, Canada
jrpiano at win.eastlink.ca
----- Original Message ----- 
From: <sarah at graphic-fusion.com>
To: <pianotech at ptg.org>
Sent: Friday, July 06, 2007 2:33 PM
Subject: Re: ear buzz update


> Hi all,
>
> I keep a pretty sleepy eye on the list these days, catching one of every
> hundred or so posts.  Anyway, being an auditory physiologist, this thread
> just now caught my eye.  I'll offer what few insights I have on the 
> matter:
>
> To understand tinnitus, you have to understand something about hair cells,
> which are the sensory cells of the inner ear (functioning both for 
> auditory
> and vestibular purposes).  In the main auditory organ, the cochlea, hair
> cells are lined up along the basilar membrane.  The basilar membrane is
> long and is shaped to be roughly tuned to different frequencies/pitches in
> much the same way a soundboard is, with big, fat, floppy regions
> corresponding to low pitches on one end, and with narrow, stiff regions
> corresponding to high pitches on the other end.  Overlying the basilar
> membrane is the tectorial membrane, into which the cilia of the hair cells
> are embedded.  As the basilar membrane and tectorial membrane vibrate up
> and down, there is a shearing motion between them, resulting in a flexing
> of the hair cell cilia back and forth.  These motions result in 
> stimulation
> of the cells, causing nerve stimulation, etc.  The hair cells seem to be a
> bit more sharply tuned, somewhat like piano strings.
>
> Here's where it gets tricky:  There are two rows of hair cells.  The inner
> hair cells seem to be the sensory units.  Vibrate them, and you hear 
> tones.
> The outer hair cells (all three rows of them) are the "muscle" of the
> organ.  They respond to nervous stimulation and are driven to vibrate 
> their
> cilia, shaking the tectorial membrane, and therefore stimulating the inner
> hair cells.  Why do they do this?  They seem to provide feedback, much 
> like
> a microphone's feedback.  When sound shakes a patch of the basilar 
> membrane
> (remember, matched for frequency), the outer hair cells get all excited 
> and
> start shaking too, which accentuates and refines the response.  If the
> feedback is adjusted low enough (through neural input), then the patch 
> will
> merely ring a bit longer, more intensely, and more sharply than it would
> without the outer hair cells.  However, if the gain of the system is set
> too high, then the patch will just keep on ringing on its own.  That's
> where tinnitus comes from.
>
> To understand the system better, just imagine making an "electric piano"
> with inductance coils independently on each string of a trichord.  Two of
> the inductance coils are used to detect vibrations and actively INDUCE
> vibrations in their respective strings, providing positive feedback
> (similar to microphone feedback).  The inductance coil on the third string
> is used entirely as a pickup and feeds to an amp, so that we can hear the
> piano.  Now, instead of hitting the strings with a hammer, we're going to
> let soundboard vibrations drive the system.  The task of our trichord is 
> to
> detect when THAT FREQUENCY (the frequency of their tuning) is present in a
> signal.  So the soundboard is vibrated, and the strings start vibrating
> too.  If the frequency is present, the active two strings in the trichord
> will ring/whine for a short time, inducing an accentuated and prolonged
> vibration of the third (pickup) string.  (Again, the task of the system is
> to determine when that frequency is present!)  But of the feedback gain on
> the active two strings is set too high, then the strings will keep ringing
> indefinitely.
>
> So tinnitus is caused by "hyperactive" outer hair cells.  It is not
> understood whether it's because they're irritated, hypersensitive to
> stimulation, misregulated, or whatever.  However, the important thing is
> that this is a very physical thing.  Thinking the system backwards, the
> outer hair cells shake the tectorial membrane back and forth rhythmically,
> inducing a shearing motion between the tectorial membrane and basilar
> membrane.  The shearing motion, in turn, causes the basilar membrane and
> tectorial membranes to vibrate up and down.  The resulting waves travel
> down the length of the basilar membrane, creating waves in the inner ear
> fluids.  These waves impinge on the oval window, causing it to vibrate.
>>From there, the vibrations travel through the middle ear bones to the
> tympanic membrane (eardrum), inducing it to vibrate too. The end result is
> that the tympanum DOES vibrate and indeed DOES create a tiny sound in the
> ear canal that can be detected with a very sensitive microphone.  The
> ringing in your ears can actually be recorded!
>
> All this leaves open the possibility of noise cancelling technology.  One
> approach might be to introduce a microphone into the ear canal (and
> microphones can indeed be that tiny) and to selectively null out the
> selected frequency(ies) with sound introduced 180 deg out of phase.
> However, I suspect the difference in acoustic impedance between the air in
> the canal and the tympanum would make that a technically problematic
> approach.
>
> A better approach might be laser interferometry, whereby a tiny laser beam
> can monitor the vibrations of the tympanum.  The interferometer output can
> be digitally filtered to select out the target frequency(ies), and then
> sound can be introduced 180 deg out of phase to cancel the measured
> vibrations of the tympanum at that(those) frequency(ies).  Of course it's
> not as easy as all that, but that would be one promising approach.
>
> So I guess the up-shot is that it probably CAN be done, if someone cares
> enough to pay the money to develop the system.  Beyond making tuning much
> easier for piano technicians, I'm sure there would be a lot of tinnitus
> sufferers who would enjoy the relief.  Of course that would require 
> wearing
> a hearing aid-like device constantly, and I'm not sure who would be 
> willing
> to do that.  I think most tinnitus sufferers simply "tune out" the ringing
> they hear.  In fact I suspect MOST people have some degree of tinnitus but
> simply don't think about it.  Me?  Oh yeah, now that the subject has come
> up, I hear a few frequencies going in the backdrop.  But if you were to 
> ask
> me on a given day whether I suffer from tinnitus, I'd probably say "no,"
> without really pausing to listen first.
>
> Hope that helps.
>
> Personal OT update, for those of you who might write off list:  I'm still
> doing fine.  I'm still just as busy as ever -- even more so now.  However,
> I'm happy and healthy.  I haven't had any more time to work on my piano.
> I'm lucky these days even to have time to practice.  But I still manage
> enough miscellaneous moments of down time to keep my sanity -- mostly with
> boating these days, since that seems to be the most common stress-relief
> denominator in this family.  ;-)
>
> Take care, y'all!
>
> Peace,
> Sarah
>
>
>
>
>
> Original Message:
> -----------------
> From: John Ross jrpiano at win.eastlink.ca
> Date: Thu, 05 Jul 2007 21:45:49 -0300
> To: pianotech at ptg.org
> Subject: Re: ear buzz update
>
>
> I realize that.
> My tone is constant in pitch.
> I had a signal generator producing a tone, years ago when it first 
> started,
> and I worked on electronic organs.
> I recollect, that I could zero beat it, at a frequency, about A5.
> John M. Ross
> Windsor, Nova Scotia, Canada
> jrpiano at win.eastlink.ca
> ----- Original Message ----- 
> From: "Mark Purney" <mark.purney at mesapiano.com>
> To: "Pianotech List" <pianotech at ptg.org>
> Sent: Thursday, July 05, 2007 8:07 PM
> Subject: Re: ear buzz update
>
>
>> Such a device would only work if we had a way for it to "hear" the
>> tinnitus noise exactly as you are hearing it. This would be the only way
>> to produce a cancellation signal that is perfectly matched in frequency,
>> but out of phase with, the original noise. Otherwise, you would get
>> phasing or beats, and/or end up doubling the noise.
>>
>> John Ross wrote:
>>> *How about a noise cancelling device, that is manually controlled.*
>>> *I am lucky enough, that with my tinnitus, I just 'tune it out'.*
>>> *Brings to mind the way someone doesn't listen to ones mate, but just
>>> says ugh, ugh.*
>>> *Selective hearing, does work, with practise.*
>>> *We train our ears, to listen for certain partials, so the opposite
>>> should be possible.*
>>
>>
>> -- 
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>
>
>
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