TIme shifting an audio in a frequency domain

Hi guys, newbie here. Needed to help on this, not sure if it is possible to acheive.

I am trying to do a time shift in freq domain on one of the audio so this part of the code i did so far. reading an audio can put into window frame form.

[data,fs] = audioread('audio.wav');
no_frame = 10;
datalength = length(data);
framesize = floor(datalength/no_frame);
temp = 0
for i = 1 : no_frame
   frames(i,:) = data(temp + 1 : temp + framesize);
   temp = temp + framesize;
end

tried doing this line but seem to have problem:

y(i,:) = yp(i,:).*exp(-j*2*pi*f*(1/fs));

Appreatiate any suggestion. Thank you.

Answer 1

[Prabhan Purwar]

Hey,

The following code illustrates the Time-shifting of a signal in the frequency domain.

[data,fs] = audioread('FemaleSpeech-16-8-mono-3secs.wav');
no_frame = 10;
datalength = length(data);
N = floor(datalength/no_frame);  %Framesize
temp = 0;
for i = 1 : no_frame
   frames(i,:) = data(temp + 1 : temp + N);
   temp = temp + N;
end
 
i=1;               %for 1st frame
t=400;                
yi=frames(i,:);
yp(i,:)=fft(yi);
y(i,:) = exp(-1i*2*pi/N*(0:N-1)*t).*yp(i,:);
rslt(i,:)=ifft(y(i,:),'symmetric');
 
plot(yi);
figure
plot(rslt(i,:));

Output:

Refer to the following links for further information:

• https://www.mathworks.com/help/matlab/ref/fft.html(FFT)
• https://www.mathworks.com/help/matlab/ref/ifft.html(IFFT)

[Yvonne Haesevoets]

I tried applying --like you did-- this property of the DTFT to operate a shift in time by a non-integer number of samples, but I was missing one element : 'symmetric'. It makes perfect sense.

It works like a charm now --thank you !