fs = 11025;
dur = 2;

a = 800;
fc = 4;
Ac = 200;

%a=-400;
%b=2000;

tt = 0:1/fs:dur;

xx= cos( a*2*pi*tt + Ac*cos(2*pi*fc*tt));

soundsc(xx,fs)

spectrogram(xx, 256, 128, 256, fs,'yaxis')
