Fs=8000; %sample rate N=100; %frequency resolution [H, F] = freqz(1,a,N); %Plot the magnitude with a logarithmic scale on the y-axis semilogy(0:Fs/(N-1):Fs,abs(H)); [y,n]=max(abs(H)); disp('The peak frequency is at:'); PeakF=(n-1)*Fs/(N-1)