function [HT,T]=dtmf_DFs=8000;N=400;b_low=[0,0.67359,0];a_low=[1,-1.47820,1];b_high=[0,0.95875,0];a_high=[1,-0.56854,1];[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_D HT;