www.pudn.com > voicebox2.zip > LPCAR2DB.M

function db=lpcar2db(ar,np) 
%LPCAR2DB LPC: Convert AR coefs to power spectrum in dB DB=(AR) 
 
 
 
%      Copyright (C) Mike Brookes 1998 
% 
%      Last modified Fri Apr  3 14:57:15 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. 
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%   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. 
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[nf,p1]=size(ar); 
if nargin<2 np=p1-1; end 
ff=rfft(ar.',2*np+2).'; 
db=-10*log10(real(ff.*conj(ff))); 
if nargout==0 
   plot((0:np+1)/(2*np+2),db.'); 
   ylabel('dB'); 
end