Linked Questions
22 questions linked to/from Does Zero Padding Distort the Spectrum of a Signal?
12
votes
5
answers
823
views
A DFT “periodic inputs” question
Why do people say that the fast Fourier transform (FFT) “views”, or “interprets”, or “assumes” its input sequence is periodic? I ask this question because the activities of viewing, interpreting, and ...
- 5,577
5
votes
9
answers
817
views
How Do I Measure the Time Duration of a Finite Length Discrete Sequence?
Assume I have a five-sample time-domain sequence (none of the five samples are zero valued) and the time period between each pair of samples is one second. Measured in seconds, what is the time ...
- 77
3
votes
5
answers
2k
views
Sequence expansion by zeros and interpolation - does it insert additional frequencies?
I am struggling with understanding the consequences of oversampling on the frequency spectrum of the signal.
If I understand correctly, with an oversampling rate of 8X we insert 7 new values for each ...
- 57
2
votes
3
answers
5k
views
DFT coefficients meaning?
What "are" they? What's a sensible way to interpret the coefficients (and what isn't)? To pose specifics:
DFT coefficients describe the frequencies present in a signal
They describe the ...
- 8,815
4
votes
3
answers
4k
views
FFT of a AM modulated signal
I am generating an AM modulated sinusoidal wave. The carrier frequency is set at $1000 \ \rm Hz$; the modulation frequency is set to $40 \ \rm Hz$ and $100 \%$ of the amplitude is modulated.
I ...
- 191
2
votes
2
answers
3k
views
DFT of pure sinusoidal wave
I'm writing a program in which you can synthesize waves by adding to a sound's Fourier transform, and then inverse the transform to get the modified sound. In order to do this, I need to know what to ...
- 121
4
votes
1
answer
2k
views
PyWavelets CWT: normalization? Vs Scipy?
Related. The equation being implemented normalizes by sqrt(1 / scale):
$$
C_{a, b} = \frac{1}{\sqrt{a}} \sum_k s(k)\left( \int_{-\infty}^{k+1} \overline{\psi \left(\...
- 8,815
3
votes
3
answers
203
views
Resource recommendations to learn audio processing
I'm looking for some good resources to learn audio processing for a machine learning task based on classification of users as either 'COVID-19 positive' or 'COVID-19 negative' based on their cough ...
- 33
3
votes
3
answers
805
views
FFT for long waveform
I should take FFT of a very long vector of length 1,636,399,763 (i.e. length order is 10^9) preferably in MATLAB. However, on 128 GB RAM, my code throws ...
- 31
5
votes
1
answer
452
views
Why DFT is used for approximating CTFT when you can approximate CTFT-integral itself?
I was using MATLAB for approximating FTs. Why DFT is used if we can approximate the transform-integration using summation.
- 185
1
vote
1
answer
885
views
How is wavelet center frequency computed?
PyWavelets (1) takes index of max DFT magnitude, (2) adds 1 to it, (3) divides by domain, which is the range of input values to the wavelet ("support"). ...
- 8,815
4
votes
2
answers
343
views
Real time FFT - Wouldn't zero-padding a signal at the end distorts the output?
I have looked at previous similar questions, but I am still not very clear on this. Most real-time or otherwise fft functions suggest adding zeros at the end of the input to make the sample size an ...
- 41
1
vote
3
answers
435
views
Unexpected imaginary part in the fft of a zero-padded cosine
I simulated a cosine waveform $ y = \cos(\omega t) $ and I applied the FFT algorithm to it. As expected, I have a frequency peak at $\pm \omega$ only in the real part, and nothing in the imaginary ...
- 119
2
votes
2
answers
157
views
FFT of 2 sine tones using windowing and zero padding. Wrong FFT amplitude
Here is my attempt to perform an FFT on a random signal with 2 tones in which I applied zero padding AFTER windowing.
(I did not apply zero padding before windowing because that would suggest that the ...
- 135
1
vote
1
answer
397
views
Zero padding DFT intuition
I'm trying to grasp some intuition about why zero-padding the time domain sequence $x[n]$ interpolates the frequency domain bins of the $DFT\{x[n]\} = X[k]$ and how does this relate to the $DTFT$ of $...
- 267