MEL2FRQ Convert Mel frequency scale to Hertz FRQ=(MEL)
frq = mel2frq(mel) converts a vector of Mel frequencies
to the corresponding real frequencies.
mr gives the corresponding gradients in Hz/mel.
The Mel scale corresponds to the perceived pitch of a tone0001 function [frq,mr] = mel2frq(mel) 0002 %MEL2FRQ Convert Mel frequency scale to Hertz FRQ=(MEL) 0003 % frq = mel2frq(mel) converts a vector of Mel frequencies 0004 % to the corresponding real frequencies. 0005 % mr gives the corresponding gradients in Hz/mel. 0006 % The Mel scale corresponds to the perceived pitch of a tone 0007 0008 % The relationship between mel and frq is given by: 0009 % 0010 % m = ln(1 + f/700) * 1000 / ln(1+1000/700) 0011 % 0012 % This means that m(1000) = 1000 0013 % 0014 % References: 0015 % 0016 % [1] S. S. Stevens & J. Volkman "The relation of pitch to 0017 % frequency", American J of Psychology, V 53, p329 1940 0018 % [2] C. G. M. Fant, "Acoustic description & classification 0019 % of phonetic units", Ericsson Tchnics, No 1 1959 0020 % (reprinted in "Speech Sounds & Features", MIT Press 1973) 0021 % [3] S. B. Davis & P. Mermelstein, "Comparison of parametric 0022 % representations for monosyllabic word recognition in 0023 % continuously spoken sentences", IEEE ASSP, V 28, 0024 % pp 357-366 Aug 1980 0025 % [4] J. R. Deller Jr, J. G. Proakis, J. H. L. Hansen, 0026 % "Discrete-Time Processing of Speech Signals", p380, 0027 % Macmillan 1993 0028 % [5] HTK Reference Manual p73 0029 % 0030 0031 0032 0033 % Copyright (C) Mike Brookes 1998 0034 % Version: $Id: mel2frq.m 713 2011-10-16 14:45:43Z dmb $ 0035 % 0036 % VOICEBOX is a MATLAB toolbox for speech processing. 0037 % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 0038 % 0039 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0040 % This program is free software; you can redistribute it and/or modify 0041 % it under the terms of the GNU General Public License as published by 0042 % the Free Software Foundation; either version 2 of the License, or 0043 % (at your option) any later version. 0044 % 0045 % This program is distributed in the hope that it will be useful, 0046 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0047 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0048 % GNU General Public License for more details. 0049 % 0050 % You can obtain a copy of the GNU General Public License from 0051 % http://www.gnu.org/copyleft/gpl.html or by writing to 0052 % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 0053 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0054 persistent k 0055 if isempty(k) 0056 k=1127.01048; 0057 end 0058 frq=700*sign(mel).*(exp(abs(mel)/k)-1); 0059 mr=(700+abs(frq))/k; 0060 if ~nargout 0061 plot(mel,frq,'-x'); 0062 xlabel(['Frequency (' xticksi 'Mel)']); 0063 ylabel(['Frequency (' yticksi 'Hz)']); 0064 end