function [HT,T]=dtmf_3Fs=8000;N=400;b_low=[0,0.52049,0];a_low=[1,-1.70774,1];b_high=[0,0.91682,0];a_high=[1,-0.79862,1];[H1,T]=impz(b_low,a_low,N,Fs);[H2,T]=impz(b_high,a_high,N,Fs);HT=H1+H2;soundsc(HT);save dtmf_data_3 HT;