Linked Questions

58
votes
8answers
93k views

How do I implement cross-correlation to prove two audio files are similar?

I have to do cross correlation of two audio file to prove they are similar. I have taken the FFT of the two audio files and have their power spectrum values in separate arrays. How should I proceed ...
18
votes
2answers
5k views

Frequency-domain zero padding - special treatment of X[N/2]

Suppose we wish to interpolate a periodic signal with an even number of samples (e.g. N=8) by zero-padding in the frequency domain. Let the DFT X=[A,B,C,D,E,F,G,H] ...
8
votes
2answers
17k views

Why images need to be padded before filtering in frequency domain

In image processing books , we are told that Images need to be padded while doing filtering in the frequency domain. Why we need that zero padding ?
8
votes
2answers
6k views

FFT of size not a power of 2

My question is regarding the input size of a signal which is not a power of 2 and we have to take the fft of it. Some solutions say that suppose if we want to take the fft of 1800 we should zero pad ...
6
votes
1answer
799 views

How to choose a windowing function when performing a Chirp $\mathcal Z$-transform?

I've got some data sampled at 32 Hz. The only interesting stuff is happening between about 0-8 Hz and I've got to do real time batch processing and detect events with a delay of no more than a second. ...
5
votes
3answers
4k views

Zero Padding in FFT

whats is the effect of pading zeroes to a sequence in FFT? for eg: x[n]=[2 3 4 5] corresponds to X[K]=[14 -2+2i -2 -2-2i] while x[n]=[2 3 4 5 0 0 0 0] corresponds to X[K]=[14 0.58-9.65i -2+2i -3.414+...
5
votes
3answers
8k views

Advantages/disadvantage of zero padding

I would like to know what are the advantages/disadvantage of zero padding with respect to frequency measurement and amplitude measurement
4
votes
1answer
3k views

What happens when N increases in N-point DFT [duplicate]

I am curious about DFT, and I wrote a simple MATLAB code to test what happens when $N$ increases. I took a rectangular signal with length $L=15$, an then found th DFT of 16, 32 and 64 points. I looked ...
3
votes
3answers
5k views

Zero-pad before or after windowing for FFT

What's the correct way. Should I zero-pad a signal before or after applying a windowing function?
3
votes
3answers
3k views

disadvantages of FFT, it can not extract enough frequencies without enough samples

Let's say sampling rate is $Fs = 44\mathtt{kHz}$, now I have $N = 2048$ samples, then I can get $N/2 + 1 = 1025$ frequencies. I'm confused by Matlab's FFT documentation that says the frequencies are ...
3
votes
2answers
943 views

The frequency response function (FRF) fails to detect the antiresonance of a system

I am trying to identify a vibrational systems by computing the frequency response function (FRF) of the system when a chirp signal is applied to its input. After comparing the FRF computed and the ...
2
votes
0answers
249 views

Is there any problem with my FFT method?

I am trying to analysis a system by Fourier Transform. my system has 3 dominant modes. (1,0.05) (0.51,0.01),(0.46,0.01) the pairs are defined as (freq,damping_ratio) I've got those result with ...
1
vote
2answers
648 views

Mathematical justification for zero padding?

This question asks what's the point of zero padding. The accepted answer is certainly very insightful, but I don't understand a big chunk of it: Zero padding allows one to use a longer FFT, which ...
0
votes
1answer
177 views

What Is the Point of Doing the Zero Padding? [duplicate]

What are the advantages and disadvantages of doing Zero-padding, in particular the case of speech signals?
0
votes
1answer
340 views

What does it mean when you zero pad data and why does one do it? [duplicate]

I am struggling to understand what effect zero padding data would have on EMG data. How does it improve the signals? Any help in simple terms that's not too mathematical would be greatly appreciated!

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