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Re: AUDITORY Digest - 27 May 2003 to 28 May 2003 (#2003-107)


There is a record that came out in JASA, produced by Ed Villchur.

Mead Killion would have a copy, and I suspect could give you wave
file versions.


Date:    Wed, 28 May 2003 13:48:12 -0400
From:    Bob Masta <masta@UMICH.EDU>
Subject: Hearing Loss Simulations

Does anyone know where to obtain (hopefully on the Web)
.WAV files simulating what would be heard by people with
various hearing losses, including cohlear implant users?


Robert Masta

         D A Q A R T A
Data AcQuisition And Real-Time Analysis
 Shareware from Interstellar Research


Please stop sending HTML format to this list (or any list for
that matter).

A good coder does, essentially, replace the FFT magnitude with an
excitation pattern. The accuracy in doing this however is no better
that our understanding of the excitation pattern, and the details
of how it is generated. There are several issues. For example,
(1) what exactly is the critical bandwidth of the cochlear filters, as a
function of the intensity and level of the stimulus. We dont yet know.
(2) what is the magnitude of the neural noise associated with each
filter? Is it is Poisson, as has been proposed?
(3) We need a detailed model of detection of signals at threshold, in
the presents of other masking tones. This model must accurately model
the upward spread of masking for complex signals. I dont think we are
there yet. The best model to date is the one by M. Heinz (ARLO).

We have a way to go yet before we can accurately calculate the masking
pattern for a complex stimulus.

Jont Allen

Date:    Wed, 28 May 2003 10:46:17 -0700
From:    Fa Long Luo <falong.luo@QSTECH.COM>
Subject: Can Audio be further Compressed by Replacing FFT Magnitude Spectrum
         with Excitation Pattern

Dear Experts and Lists,
   I would  be most grateful if you could give any comment, advice and =
further information about the idea: further audio compression  with =
excitation pattern  replacing  the FFT magnitude spectrum used in =
calculating masked threshold and the related bit allocation in current =
audio codecs such as AC3 and AAC. . The motivation for this thought is =
on the basis of  the fact that excitation patterns are much flatter than =
the magnitude spectrum.
   Thank you  for your kind attention.
    I am looking forward to hearing your Reponses.

Fa-Long Luo