[sdiy] Phase shifts and instantaneous frequency

[cheater cheater]

Rainer,

indeed our hearing does great stuff mangling the sound that comes in,
before it reaches the nerves that later transmit to the brain.
Frequency-specific hearing aids are indeed doing a lot of their work
in the frequency domain, but this does not say that the auditory
system itself works this way?The frequency-dependent workings of the
hearing aid are, as I understand, usually targeted at the
inefficiencies of the mechanical-accoustical part of the hearing
system. What's going on further, in the brain, can - as I understand
it - be probed through statistical methods, and this is a very
difficult way to gain insight. There's no doubt that the initial
accoustic path can be easily understood.
But I'm sure that it doesn't do 'fourier analysis on the signal' as
much as a violin body doesn't? I think this is a good comparison,
because in both instances the input and output are mechanical waves.
What are your thoughts on this?

Cheers
Damian

On 7/17/08, Rainer Buchty <rainer at buchty.net> wrote:
> On Wed, 16 Jul 2008, cheater cheater wrote:
>
>  > To answer: I said 'ears doing fourier transform' makes no sense simply
>  > as that: because it did not for me. Fourier analysis is a numerical
>  > tool that allows you to change the form of a signal in a very certain
>  > way. The human brain's psychoaccoustics may or may not display similar
>  > behaviour under certain conditions, but it is nearly impossible to
>  > prove that the way the human auditory system works is anywhere near
>  > frequency-oriented.
>
>
> Oh, you mean all these hearing aid manufacturers working on
>  frequency-dependent hearing aids and implants are on the wrong track?
>
>  Tell you something: how the ear detects and processes frequencies is
>  understood rather well. Your daily dose of MP3 makes use of that
>  knowlege, for instance.
>
>  The model of the ear can be roughly seen as a series of bandpass
>  filters; unfortunately, the signalling behind can either transport fine
>  frequency resolution or high volume, not both, which is why louder
>  frequency domains silence neighbored ones w/ lower signal levels. (And
>  I'll happily pass you the slides of our institute's dept. which deals
>  with that kind of stuff.)
>
>  What the *brain* makes out of that is something completely different.
>  It's not even too well understood what those intermediate nerve nodes do
>  on the way from ear to brain -- what seems to be, though, is that
>  permanent tinnitus typically is a product of those "inner" nodes, i.e. a
>  (somewhat permanent) glitch in the signal processing behind.
>
>
>  Rainer
>
>
>