From a limited number of microphones, it is possible to
extract more than this number of signals - that's basically what stereo and
ambisonics (not to mention transaural) does. Using several spaced capsules (as
against coincident or virtually coincident) can work in higher order
ambisonics, theoretically, though there are some 'noise' issues at present.
Whtether the capsules are directional or omni (or 'in between' - semi-cardioid
as used in the SoundField Mic), it's not necessary to assume that switching
between capsules is what you want to do. - you're actually just looking for a
signal that is optimised for a particular source. By treating your signals in a
matrixed fashion, you can rapidly try out succesions of 'decodes' (and these can
have frequency dependent components, too). Nevertheless, who or what is
steering? - is this a learning algorithm designed to mimic scene analysis? - it
would seem that you need a best-fit explanation for the entirety of components
in a detected sound field, otherwise you'll have 'bits left over' - isn't that
----- Original Message -----
Sent: 25 March 2005 17:43
Subject: Re: ICA, a key to solve the
puzzle of hearing
Toth Laszlo wrote:
On Fri, 25 Mar 2005, Guoping Li wrote:
ICA was designed to solve the problem of cocktail party effect using
higher order statistical methods. Is it possible that we can use this
technique and implement it in the hearing aid or cochlear implant?
As far as I remember, when ICA is used for blind signal separation, it
needs at least N input signals (for example, from a microphone array) for
extracting N independent components.
That's true, but there is no reason a priori why one
shouldn't build a device that incorporates dozens of microphone capsules in
the users clothing, and that could separate dozens of different sources. Then
you'd just need a little switch that allows you to quickly scan through those
separated sources to find the one you want to listen to. It wouldn't be very
"biological", but it might nevertheless work quite well.
Dr. Jan Schnupp
University Laboratory of Physiology St Peter's College
Oxford University New Inn Hall Street
Parks Road, Oxford OX1 3PT, UK Oxford OX1 2PL
Tel (01865) 272513 Tel (01865) 278889
Fax (01865) 272469
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