Re: Critical bands v hearing loss

[beaucham <beaucham@xxxxxxxxxxxxxxxxxxxxxx>]

Dear List,

I'm not sure about the hearing-aid case, but in the case of normal
listening, this is a personal interest of mine. I have been 
interested in spectral data reduction for the dual purpose of 
better understanding musical timbre and for developing better 
methods of musical sound synthesis. Last spring a colleague and
I did an experiment on critical band data reduction of some 
musical tones, and I gave a paper on it at the spring ASA meeting:

Beauchamp, J. W. and Horner, A. B. (2005). "Effect of critical-
band smoothing of musical instrument spectral data" (A), 
J. Acoust. Soc. Am. 117 (4), Pt. 2, 2476.

Two methods were used: 1) replacing the spectra within critical 
bands by static spectra with common amplitude and frequency
controls; 2) smoothing instantaneous spectra with critical band
filters. The Zwicker/Terhardt critical band formula (JASA, Nov.,
1980) was used, but for both cases we employed a bandwidth 
multiplier in order to get a discrimination-vs.-multiplier
psychometric curve. The preliminary results showed that at least 
for "young acute normal" ears, you need bands narrower than 
critical band in many cases, particularly for low piano tones. 
Nevertheless, from casual listening it appears that CB data 
reduction may be acceptable in many cases, e.g., in comparison 
to MP3 data reduction.

Jim Beauchamp
Univ. of Illinois at Urbana-Champaign

>From: Vinay SN <vinaysn@xxxxxxxxx>
>Date: Thu, 22 Sep 2005 01:04:59 -0500
>To: AUDITORY@xxxxxxxxxxxxxxx
>Subject: Re: Critical bands v hearing loss
>Comments: To: "Richard H." <auditory@xxxxxxxxxxxxxx>
>
>Dear list,
>
>The human ear can only make sense of one signal per critical band. For
>example, if two sine tones of 100Hz and 110Hz are played, two distinct
>tones are not heard. This is because the critical bandwidth at 100Hz is
>about 80Hz, and the two tones would be within the same critical band; one
>will only hear two distinct tones when the two excitations exist in
>separate critical bands. Hence there is no point in having controllable
>bands which are finer in resolution  than a critical band.
>
>Vinay S.N (M.Phil, M.Sc)
>
>Doctoral Student in Audiology,
>
>AIISH, Mysore - 6.
>
>  ----- Original Message -----
>  From: "Richard H."
>  To: AUDITORY@xxxxxxxxxxxxxxx
>  Subject: Critical bands v hearing loss
>  Date: Wed, 21 Sep 2005 15:14:00 +0100
>
>Hi, In hearing aids & similar band-based audio processors, is there
>likely to be any point in having controllable bands which are finer in
>resolution  than a critical band? Thanks, regards, Richard