Matlab带阻滤波器设计问题

Question

下面的代码中出了什么问题呀？滤波前和滤波后频谱没发生什么变化，为什么会滤不了波

%设计带阻滤波器
[x0,Fs]=audioread('luyin.wav');
N=length(x0);
Fs2=8000;
fp1=1000;
fp2=3500;
fs1=1500;
fs2=2800;
Wp1=fp1/Fs2*2*pi; 
Wp2=fp2/Fs2*2*pi; 
Ws1=fs1/Fs2*2*pi; 
Ws2=fs2/Fs2*2*pi; 
Wp=[Wp1,Wp2];
Ws=[Ws1,Ws2];
Rp=0.01;
Rs=80;
[n,Wn]=buttord(Wp/pi,Ws/pi,Rp,Rs,'s');
[b,a]=butter(n,Wn,'stop');
% [H,w]=freqz(b,a);
% magnitude=20*log10(abs(H));
% plot(w/(2*pi)*Fs2,magnitude)

y=filter(b,a,x0);
Y=fft(y,N); 
n=(1:N);
f=n*Fs/N;
subplot(3,1,2)
plot(f,abs(Y)) 
xlabel('f/Hz');
ylabel('magnitude');
title('滤波后音频信号傅里叶变换后的幅度') 

Answer 1

https://blog.csdn.net/Summertrainxy/article/details/103611954?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522167124215716782425143372%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=167124215716782425143372&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduend~default-1-103611954-null-null.142^v68^control,201^v4^add_ask,213^v2^t3_control2&utm_term=%E5%B8%A6%E9%98%BB%E6%BB%A4%E6%B3%A2%E5%99%A8%E8%AE%BE%E8%AE%A1&spm=1018.2226.3001.4187