gistfile1.matlab

% shepardtones.m - plays the shepard tones
% based on an example I found here: http://hebb.mit.edu/courses/9.29/2003/athena/auditory/matlab/shepardtones.m

% adjustable parameters
max_time = 2; % time for each tone
max_repeat = 3; % number of loops
A = 440;     % "base frequency"
num_harm = 7; % number of harmonics used for each tone
sigmasq = 1; % variance of the amplitude for each partial

fs = 8192;   % the sampling rate
dt = 1/fs;
t = [0:dt:max_time];

k = -2:(-2+num_harm);
m = 2^(1/12);     % semitones
% sigmasq = 1;
rep = [];

for j = 0:11
y = zeros(size(t)); % initialize the tone vector
   for i = 1:num_harm         % use each harmonic in k
       f_ij = 2^k(i)*(A*(m^j));  % the frequency of this component
       amp = exp((-1/2*sigmasq)*(log2(f_ij/A))^2);
      y = y + amp*cos(2*pi*f_ij*t);
   end;
rep = [rep y];  % append the finished tone to the tone vector
end;


rep = repmat(rep,1,max_repeat);  % repeat max_repeat times
soundsc(rep,fs);                 % play it