# Questions tagged [fft]

The fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse.

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### How to generate time-series from a given one-sided PSD?

Generating time series from a given PSD has been discussed in this and some other forums already (which I've referred some of them below) but almost all of them are mostly descriptive and none of them ...
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### Understanding FFT bins interpretability

I am familiar with the continuous Fourier transform yet the more I try to understand FFT, the more I'm confused. If we've got a discrete N sample signal, FFT is a faster way to calculate DFT. If ...
1 vote
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### FFT Artifacts and their cause beyond frequency resolution

I am trying to work through an issue with an FFT for audio : I have no spectral leakage while playing back audio, but the moment I change or zero out a value in any of the FFT bins, artifacts are ...
1 vote
241 views

### Why do some signals have "DC component" whilst others don't?

I am analyzing a series of oscillating data of items that gradually become less "floppy"/oscillatory and I have observed that those items that are less floppy/oscillatory tend to have, what ...
1 vote
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### How do I convert the Amplitude from Power/Amplitude spectral density?

I recently started working on PSD of seismic signals. PSD signal can be expressed in 2 ways. One in ($PSD=g^2/Hz$) and other in $PSD=((meter/sec.^2)^2/Hz)$ and $ASD = \sqrt(PSD)$. More details have ...
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### Help Understanding FFT Plot?

I want to analyze FFT and Harmonics of my signal. As a proof of concept I tested FFT against standard signal. I am unable to understand why the frequency output is going to -1. Shouldn't it be +1 at <...
33 views

### Improving the intuition for the 2d fourier transform

As far as I understand, the 2d fourier transform is calculated as following: ...
67 views

### Can we recover $|X(k)|$, given $|x(n)|$?

Given a complex vector $x[n]$, we can find the magnitudes of the spectrum by computing: $X_m[k] = |X[k]| = |FFT[x]|$ This involves performing a complex FFT and computing the absolute value of the ...
1 vote
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### How to Calculate Frequency "X values" from a FFT/DFT Transformation

First of all I am totally new to the DSP field and I have no background in it whatsoever, but my work in biology has led me to data that would greatly benefit from DSP. Any answers devoid of specific ...
101 views

### Can I "reverse" spectral leakage by solving a linear system?

When I compute a spectrogram of (say) a piece of music, there is a lot of frequency "smearing." Often we can reasonably expect that the "true" generating process is much sparser in ...
1 vote
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### Power Spectrum for feature extraction

I want to extract frequency domain features for my machine learning model, and to do so I have calculated the power spectrum of the EMG signal. One of my first questions is that my frequency is just ...
55 views

### Should I be using FFT

I am using python (scipy.fft) to live analize EEG data. The app resonds instantl based on the signls coming from EEG (Alpha Beta...)The problem is that when I run the FFT on only 100 samples or so (...
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### mp3 encoding in the frequency domain

Let's start with an arduino signal, which can be periodic over time. When this signal is converted from analog to digital it "turns" into a series of bits. At this point, is this signal in ...