% Create 32 mel-scale filterbanks, for use on a 512-point FFT
W=melbankm(32,512,8000);
% Cut WAV into 160-sample windows, overlapping by 120 samples
FRAMES=enframe(WAV,160,40);
% Compute magnitude STFT
MSTFT=abs(fft(FRAMES,512,2));
% Multiply MSTFT times W to create mel-scale spectrogram
MELGRAM=20*log10(W*MSTFT(:,1:257)');
% Compute center frequencies, in Hertz, of each filter
FREQS=round(mel2frq([1:32]*frq2mel(4000)/33));
% Compute time alignments, in milliseconds, of each frame
TIMES=[-140:5:140];
% Create an image plot of the mel-scale spectrogram
imagesc(TIMES,FREQS,MELGRAM);
% Flip the frequency axis, so low frequency is at bottom
axis xy;
%% Alternate code -- necessary only if your version of matlab has
%% the bug that causes nonlinear Y-axis to fail
imagesc(TIMES,[1:32],MELGRAM); axis xy;
YTick=get(gca,'YTick');
YTickLabel='';
for I=YTick, YTickLabel=strvcat(YTickLabel,sprintf('%d',FREQS(I))); end
set(gca,'YTickLabel',YTickLabel);