source: birds/domilbirds.m @ 59

% directory where the WAV-files of the birds are stored:
dpath = fullfile(mildatapath,'birds');

fname = 'PC13_20090531_050000_0.wav';
%fname = 'PC8_20090531_050000_99.wav';
[signal,fs] = wavread(fullfile(dpath,'wavs',fname));

[S,f,t] = spectrogram(signal,512,256,[],fs);
fmax = 256;%Defined in paper

figure(2); clf; showspec(S,f,t);
[S,f,t] = spectrogram(signal,512,256,fmax,fs);

figure(2); imagesc(t,f,abs(S));
axis xy; xlabel('time (s)'); ylabel('freq.');

figure(3); clf; showspec(imag(S), f,t);

%%
% smooth and threshold the spectrogram?
G = fspecial('gaussian',[5 5],2); % window 5x5, sigma=2
I = imfilter(abs(S),G,'same');
t = dd_threshold(I(:),0.8);
mask = (I>t);
mask(f<2000,:) = 0;

figure(4); clf; imagesc(mask); axis xy;
% measure something:
x = regionprops(bwlabel(mask),abs(S));
y = x([x.Area]>10)



%%
s2 = specwhiten(S,fmax); 
figure(5); imagesc(t,f,s2);
axis xy; xlabel('time (s)'); ylabel('freq.');

% do the same smoothing but change the threshold
G = fspecial('gaussian',[5 5],2); 
I = imfilter(abs(s2),G,'same');
t = dd_threshold(I(:),0.95);
mask = (I>t);
mask(f<2000,:) = 0;

figure(6); clf; imagesc(mask); axis xy;    %Looks pretty similar, but less small blobs 
% measure something:
x = regionprops(bwlabel(mask),abs(s2));
y = x([x.Area]>10)