Amateur question

Steve Ungstad steve_ungstad at agilent.com
Fri Mar 17 03:15:30 EST 2000


Eckard,

I have little reason except curiosity to pursue the state of 
current theory about the cochlea. Nor do I care about details that
come from a competent mechanical analog simulation. 

Whether it is the fluids in the cochlea or other structures, the point
I wanted to make is that the system strikes me as similar to an FIR
filter.
The essentials being that any given position along the spiral is
frequency selective because the sound reaches that point via two paths.
Those two paths  reinforce the stimulation at different frequencies
along the spiral because  the velocity of one path is different than
along the other. The spiral also
creates the same effect because the outer path is longer than the inner
one.
The farther down the spiral, the greater the delay of one path relative
to the other, and hence the lower the frequency that stimulates that
spot.

I'm sure there are many details that complicate the larger picture, but
that does not negate the value this idea. Nature designs it's creation
purely on empirical results. No mathematical model ever completely
explains, well, anything, for that matter. 

For example, relativity discovered errors in classical physics, but that
does not mean that Newton was wrong. Like wise, today have found flaws
in the work of Einstein, but, again, it does not mean he was wrong. As
time passes, we refine our knowledge, but total understanding is a
infinitive that we will never reach on any subject. ( sorry for the rant
;-)

Steve Ungstad
 
> -----Original Message-----
> From: Eckard.Blumschein at e-technik.uni-magdeburg.de
> [mailto:Eckard.Blumschein at e-technik.uni-magdeburg.de]
> Sent: Thursday, March 16, 2000 3:34 AM
> To: steve_ungstad at agilent.com
> Subject: RE: Re: Amateur question
> 
> 
> Steve,
> 
> At 13:18 10.03.00 -0700, you wrote:
> >The structure appears to me to be two delay lines, forming a  
> >physical FIR filter. But this requires a transmission medium  
> >of very low velocity to accomplish this within the size of a ear.
> >
> >I was hoping, if this had not already been done, that someone  
> >would go looking for such characteristics. As you mentioned,
> >liquids generally have a much higher velocity than a gas, so  
> >the presents of an unusual material with low acoustic velocity
> >would be very significant.  
> 
> Reality is certainly somewhat different from the traditional wave
> propagation stuff you seems to stick on even if people 
> presently resort in
> reflection in order to explain DPOAE. Given there was the 
> material you are
> looking for, then it must alter its properties over a huge range.
> Experiments show that the radial velocitiy exceeds the 
> longitudinal one by
> a factor of ten, etc. 
> 
> I would recommend to you: Ask for the proceedings of the last 
> conference on
> cochlea mechanics last year in Japan. I would be interested in the
> bibliographical data in order to get this proceedings, too. 
> You might also
> find many papers from the annual ARO meetings.     
>






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