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
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%   This program is distributed in the hope that it will be useful,
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%   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%   GNU General Public License for more details.
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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