www.pudn.com > voicebox2.zip > FRQ2ERB.M

function erb = frq2erb(frq) 
%FRQ2ERB  Convert Hertz to ERB frequency scale ERB=(FRQ) 
%	erb = frq2erb(frq) converts a vector of frequencies (in Hz) 
%	to the corresponding values on the ERB-rate scale on which 
%  	the human ear has roughly constant resolution as judged by 
%  	psychophysical measurements of the cochlear filters. 
 
%	We have df/de = 6.23*f^2 + 93.39*f + 28.52 
%	where the above expression gives the Equivalent Rectangular 
%	Bandwidth (ERB)in Hz  of a human auditory filter with a centre 
%	frequency of f kHz. 
% 
%	By integrating the reciprocal of the above expression, we 
%	get: 
%		e = a ln((f/p-1)/(f/q-1)) 
% 
%	where p and q are the roots of the equation: -0.312 and -14.7 
%  	and a = 1000/(6.23*(p-q)) = 11.17268 
% 
%	We actually implement e as 
% 
%		e = a ln (1 + b*f/(f+c)) 
% 
%	where b = q/p - 1 = 46.06538 
%	      c = -1000q = 14678.49 
%	and f is in Hz 
% 
%	References: 
% 
%	  [1] B.C.J.Moore & B.R.Glasberg "Suggested formula for 
%		calculating auditory-filter bandwidth and excitation 
%		patterns", J Acoust Soc America V74, pp 750-753, 1983 
% 
%	  [2] O. Ghitza, "Auditory Models & Human Performance in Tasks 
%		related to Speech Coding & Speech Recognition", 
%		IEEE Trans on Speech & Audio Processing, Vol 2, 
%		pp 115-132, Jan 1994 
%	 
 
 
 
%      Copyright (C) Mike Brookes 1998 
% 
%      Last modified Fri Apr  3 14:57:14 1998 
% 
%   VOICEBOX home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 
% 
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%   This program is free software; you can redistribute it and/or modify 
%   it under the terms of the GNU General Public License as published by 
%   the Free Software Foundation; either version 2 of the License, or 
%   (at your option) any later version. 
% 
%   This program is distributed in the hope that it will be useful, 
%   but WITHOUT ANY WARRANTY; without even the implied warranty of 
%   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
%   GNU General Public License for more details. 
% 
%   You can obtain a copy of the GNU General Public License from 
%   ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to 
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
erb=11.17268*log(1+46.06538*frq./(frq+14678.49));