% butter_filter.m  4th order Butterworth filter
[b, a] = butter(4, [0.01, 0.1]);
% load handel
y = randn(1,16000);
y = y(1:16000);
vo_t = filter(b,a,y);  % Apply digital filter
y = vo_t;
y = y*10;
sound(y)
plot(t,vo_t)