% Computation of ST-ZCR and STE of a speech signal.
%
% Functions required: zerocross, sgn, winconv.
%
% Author: Nabin Sharma
% Date: 2009/03/15

[x,Fs] = wavread('so.wav'); % word is: so
x = x.';

N = length(x); % signal length
n = 0:N-1;
ts = n*(1/Fs); % time for signal

% define the window
wintype = 'rectwin';
winlen = 201;
winamp = [0.5,1]*(1/winlen);

% find the zero-crossing rate
zc = zerocross(x,wintype,winamp(1),winlen);

% find the zero-crossing rate
E = energy(x,wintype,winamp(2),winlen);

% time index for the ST-ZCR and STE after delay compensation
out = (winlen-1)/2:(N+winlen-1)-(winlen-1)/2;
t = (out-(winlen-1)/2)*(1/Fs);

figure;
plot(ts,x); hold on;
plot(t,zc(out),'r','Linewidth',2); xlabel('t, seconds');
title('Short-time Zero Crossing Rate');
legend('signal','STZCR');

figure;
plot(ts,x); hold on;
plot(t,E(out),'r','Linewidth',2); xlabel('t, seconds');
title('Short-time Energy');
legend('signal','STE');