function plotfreq
%plotfreq.m - plot the frequency responce of
%transfer function
%                -1        -2
%     b(1)+b(2)*z   +b(3)*z
%H(z)=-------------------------
%                -1        -2
%     a(1)+a(2)*z   +a(3)*z

b=[1 2 0];
a=[1 2 3];
Nfft=1024;
Fs=16000;
freqz(b,a,Nfft,Fs);