pkg load signal
[y,fs] = audioread('modulator22.wav');
audiowrite('outmodulator22.wav',y,fs/2);
n = length(y); 
t=0:1/fs:(n-1)/fs; % time range
figure;
plot(t,y);
xlabel('time (s)');
ylabel('amplitude');


[power,duration]=frequencySpectrum(y, fs, false);
figure;
plot(duration,power);