findpitch.m

滤波器的设计以及零极点对应频率响应分析

function PT=findpitch(s)
% compute the pitch of speech s
[B,A]=butter(5,700/4000);
% Butterworth digital and analog filter design and returns the filter coefficients 
% in length N+1 vectors B (numerator) and A (denominator),cutoff frequency  Wn must be 0.0 < Wn < 1.0, 
%with 1.0 corresponding to half the sample rate.
s=filter(B,A,s);
R=zeros(143,1);
for k=1:143
    R(k)=s(144:223)'*s(144-k:223-k);% the self-correlative coefficients
end
[R1,T1]=max(R(80:143));
T1=T1+79;
R1=R1/(norm(s(144-T1:233-T1))+1);
[R2,T2]=max(R(40:79));
T2=T2+39;
R2=R2/(norm(s(144-T2:233-T2))+1);
[R3,T3]=max(R(20:39));
T3=T3+19;
R3=R3/(norm(s(144-T3:233-T3))+1);
Top=T1;
Rop=R1;
if R2>=0.85*Rop
    Rop=R2;
    Top=T2;
end
if R3>0.85*Rop
    Rop=R3;
    Top=T3;
end
PT=Top;
end