MATLAB Answers

Time-shift after fft & filter?

12 ビュー (過去 30 日間)
Shaula Garibbo
Shaula Garibbo 2020 年 6 月 12 日
コメント済み: Shaula Garibbo 2020 年 6 月 12 日
I tried to implement a simple LP filter on an audio file, but I'm slightly confused by the apparent shifting of the signal in the time domain. What have I overlooked / misunderstood? Thanks.
filename = 'Raw_Wav_20180425_000226.wav';
[y,fs] = audioread(filename);
subplot(1,2,1)
plot(t,y)
xlabel('Time (s)')
ylabel('Amplitude')
title('Raw')
fmax1 = 40; %end of pass band
fmax2 = 60; %end of transition band
nt = length(y);
t = [0:nt-1]/fs;
y = y-mean(y);
dF = fs/nt;
f = -fs/2:dF:fs/2-dF;
yft = fftshift(fft(y));
I = find(abs(f)>fmax2);
yft(I) = 0;
I = find( abs(f)>fmax1 & abs(f)<=fmax2 );
yft(I) = yft(I) .* hanning(length(I));
y = ifftshift(ifft(yft));
subplot(1,2,2)
plot(t,y)
xlabel('Time (s)')
ylabel('Amplitude')
title('Post-filter')

採用された回答

Sugar Daddy
Sugar Daddy 2020 年 6 月 12 日
As you have taken fft first and then fftshift, so if you want to do inverse of this, you need inverse of fftshift first as it is performed at the end. so the order of inverse must be
  1. ifftshift
  2. fft
  1 件のコメント
Shaula Garibbo
Shaula Garibbo 2020 年 6 月 12 日
Thank you very much!

サインインしてコメントする。

その他の回答 (0 件)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by