This documentation page applies to an outdated major AMT version. We show it for archival purposes only.
Click here for the documentation menu and here to download the latest AMT (1.6.0).
function outsig = transposedtone(siglen,fc,fm,fs,varargin)
%TRANSPOSEDTONE Transposed tone test stimuli
% Usage: ts = transposedtone(fc,fm,dur,fs);
%
% Input parameters:
% siglen : Length of signal
% fc : Vector of carrier frequencies (Hz)
% fm : Vector of modulation frequencies (Hz)
% fs : Sampling frequency (Hz)
%
% Output parameters:
% outsig : transposed tone (column vector)
%
% TRANSPOSEDTONE(siglen,fc,fm,dur,fs) generates a transposed tone test
% stimuli as defined in Kolrausch et. al (1997).
%
% By default, the output is normalized to have an RMS value of 1, but this
% can be changed by passing any of the flags from the normalize function.
%
% Some example parameters as used in a study by Santurette:
%
% siglen = 44100;
% fc = 5000;
% fm = 435;
% fs = 44100;
% outsig = transposedtone(fc,fm,dur,fs);
%
% References:
% A. Kohlrausch, R. Fassel, M. Heijden, R. Kortekaas, S. Par, A. Oxenham,
% and D. Puschel. Detection of tones in low-noise noise: Further evidence
% for the role of envelope fluctuations. Acta Acustica united with
% Acoustica, 83(4):659-669, 1997.
%
% A. Oxenham, J. Bernstein, and H. Penagos. Correct tonotopic
% representation is necessary for complex pitch perception. Proceedings
% of the National Academy of Sciences, 101(5):1421-1425, 2004.
%
%
% Url: http://amtoolbox.sourceforge.net/amt-0.9.5/doc/signals/transposedtone.php
% Copyright (C) 2009-2014 Peter L. Søndergaard.
% This file is part of AMToolbox version 1.0.0
%
% 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 3 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 should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% Author: Sébastien Santurette 2009
if nargin<4
error('Too few input parameters.');
end;
definput.import={'normalize'};
definput.importdefaults={'rms'};
[flags,keyvals]=ltfatarghelper({},definput,varargin);
% time vector
t = (0:siglen-1)/fs;
% number of tones
n = length(fc);
outsig = zeros(siglen,1);
for ii = 1:n
% carrier tone
carrier = cos(2*pi*fc(ii)*t);
% "modulator"
hrsine = sin(2*pi*fm(ii)*t);
% half-wave rectify the modulator
hrsine = max(0,hrsine);
% Compute coefficients for low-pass filtering
fcuth = .2*fc(ii)/(fs/2);
[b,a] = butter(4,fcuth,'low');
% Low-pass filter the modulator
hrsine = filter(b,a,hrsine);
% Add the carrier*modulator to the transposed tone
outsig = outsig+(carrier.*hrsine)';
end;
outsig=normalize(outsig,flags.norm);