Kamil Wojcicki

If all you want is a warping other than the mel scale, then the function is written to support that, i.e., no need to change trifbank.m. I would just pass different warping / unwarping functions to it:

- in MATLAB type in: help trifbank

- then try the example given there ( it will poduce a mel filterbank ), e.g.:

fs = 16000; % sampling frequency (Hz)
nfft = 2^12; % fft size (number of frequency bins)
K = nfft/2+1; % length of each filter
M = 23; % number of filters

hz2mel = @(hz)(1127*log(1+hz/700)); % Hertz to mel warping
mel2hz = @(mel)(700*exp(mel/1127)-700); % mel to Hertz warping

% Design mel filterbank of M filters each K coefficients long,
% filters are uniformly spaced on the mel scale between 0 and Fs/2
[ H1, freq ] = trifbank( M, K, [0 fs/2], fs, hz2mel, mel2hz );

hfig = figure('Position', [25 100 800 600], 'PaperPositionMode', ...
'auto', 'Visible', 'on', 'color', 'w'); hold on;

plot( freq, H1 );
xlabel( 'Frequency (Hz)' ); ylabel( 'Weight' ); set( gca, 'box', 'off');

- in the above code, the warping function are defined in following variables:

hz2mel = @(hz)(1127*log(1+hz/700)); % Hertz to mel warping
mel2hz = @(mel)(700*exp(mel/1127)-700); % mel to Hertz warping

- to use different warping functions you first have to define these, e.g., if you want uniformly spaced filters on Hz scale use:

hz2warp = @(hz)( hz );
warp2hz = @(warp)( warp );

- and make sure you then update the trifbank call with the new function handles:

[ H1, freq ] = trifbank( M, K, [0 fs/2], fs, hz2warp, warp2hz );

Hi Alecsander, you can pass color map as one of the inputs to the myspectrogram method. In the test_myspectrogram.m try, f.e.,

myspectrogram( speech.(method), fs, [22 1], @hamming, 2048, [-59 -1], false, 'hot', false, 'per' );

Alternatively you can specify color map for the current figure after calling the myspectrogram method, e.g.,

myspectrogram( speech.(method), fs );
colormap hot;
%colormap jet;

See also http://www.mathworks.com/help/techdoc/ref/colormap.html