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Questions tagged [stft]

Short-Time Fourier Transform

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writing from STFT to audio using ISTFT adding harmonics to audio not present before

I'm doing quite a bit of the samething as I wrote in this post here : Shifting frequency peaks such that w[i] moves to w[i/n] using STFT and IFFT I'll quote from it here to present the issue I now ...
Vrisk's user avatar
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Shifting frequency peaks such that w[i] moves to w[i/n] using STFT and IFFT

I am trying to do a kind of frequency compression on say 20 most energetic frequencies in a particular slice of a STFT. If w[i] is the frequency peak for a slice of STFT at a particular time, then I ...
Vrisk's user avatar
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Calculating PSNR using STFT of sampled signal

I have a baseband IQ sampled signal from a Pluto SDR with a bandwidth B and also fs = B, how can I calculate its PSNR using the STFT of the signal in Matlab. Do I need to take into account the RBW of ...
Daniel Cohen's user avatar
1 vote
1 answer
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Window Type Effect on Pwelch vs ShortTimeFFT PSD Result?

I am trying to make sure I understand the output scaling of pwelch. I am using the PWelch function to compute the PSD of a signal and I have manually computed the PSD from an STFT output. The results ...
Michael's user avatar
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5 votes
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Interpolation of STFT between time and frequency bins

I am trying to identify and remove airplanes in a time series obtained at a radio meteor receiver. Here we have a spectrogram which displays the power content of my signal as a function of frequency ...
Vakeras's user avatar
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2 votes
1 answer
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what does librosa.stft do that makes it different?

My understanding of the Short Time Fourier Transform is that first I need to frame the signal and window it, after that apply an fft on these windowed frames. Using Librosa: ...
kulon one's user avatar
1 vote
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Advantage and Disadvantage using Mel Spectrograms over STFT in speech/waveform synthesis

I want to ask you a question about the waveform synthesis or more spesifically speech synthesis. Most of the state-of-the art papers use mel-spectrograms as their inputs, because it mimics the human ...
Yalçın Cenik's user avatar
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STFT normalization

In Scipy's implementation of STFT, an argument allows to scale the result as a spectrum or as a psd : ...
hugopb82's user avatar
3 votes
2 answers
105 views

Why not overlap save for inverse stft

Since STFT uses overlapped sections of the input signals and compute DFT, it resembles overlap-save method used for block convolution, instead the overlap-add method for block convolution uses non-...
Ras's user avatar
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1 answer
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reproduce Scipy's stft

I failed to reproduce Scipy's stft. When I have tried to remove all the possible modifications and go the minimal example, I converge to the following: ...
Gideon Genadi Kogan's user avatar
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How to implement STFT for processing audio [closed]

I should start this off by saying I’m a hobbyist and by no means a student. I’ve been reading “The Audio Programming Book”, and attempting to implement STFT on the stm32 based Daisy platform. In order ...
Daniel Lawler's user avatar
2 votes
1 answer
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What is the difference between STFT and Gabor filter?

My understanding is that a Gabor filter gives us information about when in the input signal does the frequency of interest (equal to the frequency of the sinusoid in the Gabor Filter) occur, thus ...
SNIreaPER's user avatar
2 votes
1 answer
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Comparing results for spectrum generating in matlab using STFT and Filterbank approach

To analyse data in the frequency domain I often use functions like stft() in Matlab. Inspired by this video and this article I have compared the results of ...
Matthias La's user avatar
1 vote
2 answers
289 views

Overall spectrum computation from Short-Time-Fourier-Transform

I am trying to computing the overall spectrum of a given signal from its Short-Time-Fourier-Transform. I am using python to do this and I wrote my function to compute the STFT: ...
Ciccios_1518's user avatar
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1 answer
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Unwindowed STFT of sine, closed form solution and insights (sliding FFT)

I seek to calculate, mathematically, the unwindowed Short-Time Fourier Transform of $$ \cos(2\pi f t + \phi) $$ i.e. any arbitrary real-valued sine: any frequency, duration, phase shift, and number of ...
OverLordGoldDragon's user avatar
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Artifact during this STFT spectrogram plotting

I am new to the field of DSP and I am currently working on implementing a real-time audio spectrogram using STFT technique. While making progress, I have encountered an issue when testing a constant ...
Sergio's user avatar
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STFT Audio processing with zeros

In this paper they preprocess an audio file with a STFT and then apply two equations to the computed matrix. I tried implementing all of it in python and used librosa for the STFT. The issue I ...
Rocket's user avatar
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STFT needs circular shift or not?

In some textbooks and websites, circular shift operation is done before doing FFT of windowed data, in the explaination, circular shift is to ensure zero-phase. But in other textbooks and websites(I ...
Xiong's user avatar
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3 answers
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Increasing STFT resolution by repeating the window? Ways to improve STFT resolution?

In theory of FT(Fourier transform) and STFT(Short Time Fourier Transform) it is said that "A narrower window gives good ...
google dev's user avatar
2 votes
2 answers
118 views

How would you compute Fourier transform of a real world signal where the signal keeps getting updated (not a static one)?

Crossposted at Electrical Engineering SE A very naive question: How do we use Fourier transform for real world signals - for which you have the information only up to the present instant (and the ...
Dynamic_equilibrium's user avatar
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1 answer
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Construction of Room Impulse Response - Short-Time-Fourier-Transform and Inverse-STFT - Matlab and NWaves (C#) Implementation

Background: I am working on a Unity Project (C#) and implementing a Room Impulse Response synthesis. I do ray tracing to create energy histogram for different bands. With these histograms it is ...
nototherwise's user avatar
4 votes
2 answers
922 views

How does the effect of windowing change with the phase of the input signal?

I am calculating the SNR (signal power to noise power) for a sine wave. I don't have an integer number of periods in the waveform being analyzed, so I am using a flattop window to reduce spectral ...
DavidG25's user avatar
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1 vote
1 answer
243 views

How do `n_fft` and `win_length` determine the window in spectrogram?

I am currently trying to understand librosa.feature.melspectrogram in a mathematical sense. In my understanding, spectrogram is based on the STFT which is for a ...
esh3390's user avatar
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1 vote
2 answers
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Scipy and Matlab Spectrogram not matching

I am trying to replicate a spectrogram from MATLAB in Python. I've read other posts but they either don't use complex data or the data doesn't match between languages. I've defined my FFT length (<...
PrematureCorn's user avatar
1 vote
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Reconstruction of batch-acquired signal

I am currently working on a project which requires evaluating slow changes over time in the magnitude of a signal's high frequency (over 10 kHz) components. This signal was acquired in tests with a 25....
G. Thaler's user avatar
6 votes
1 answer
605 views

Equivalence between "windowed Fourier transform" and STFT as convolutions/filtering

I've heard, that "windowed Fourier transform" is but one perspective on STFT, and that STFT is fundamentally convolutions of windowed complex sinusoids with the input, i.e. bandpass ...
OverLordGoldDragon's user avatar
1 vote
0 answers
36 views

How to calculate phase estimation error

I am working on speech enhancement and I want to compare the phase and magnitude between two signals. I compute the STFT for both, and comparing the magnitudes is easy via mean-squared error or some ...
Mirao Da Silva's user avatar
1 vote
0 answers
38 views

A mathematical justification of discontinuity detection using STFT

I'm trying to detect rapid changes in a one-dimensional signal say $[0,1]\ni t \mapsto f(t) \in [-1,1]$. By rapid changes, I mean corner points, edges, or sharp transitions at a point for example the ...
Zeno San's user avatar
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2 votes
2 answers
973 views

Amplitude extraction using STFT

I'm trying to recover amplitude/magnitude from an audio stream. I'm using FFT to go from time domain to frequency. If I feed in a signal of known amplitude, the results I get from either windowing or ...
dizzy's user avatar
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1 vote
1 answer
312 views

Overlap and Add/Save Inverse Short-Time Fourier transform

Edited for conciseness, please see below: Question: How does overlap and save work, in the context of array buffers? How does overlap and add work? For a specific use case involving STFT, which one is ...
HFGCS's user avatar
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3 answers
570 views

Does overlapping windows while processing a signal produce a stretched time domain?

I'm very new to signal processing and attempting to implement a spectrogram generator to learn more about DSP in general. So far, I have built up an understanding of how I might do that. Get input ...
acd's user avatar
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0 answers
223 views

difference in speed between tensorflow implementations of mfcc and stft

I am trying to preprocess audio clips for a keyword spotting task that uses machine learning models. The first step is to calculate the spectrogram starting from the waveform and in order to do so I ...
Giacomo Zema's user avatar
2 votes
2 answers
955 views

Wigner-Ville Distribution (WVD) vs STFT for Spectral Analysis

What are the Pros and Cons of using Wigner-Ville Distribution for spectral analysis of a signal vs taking the STFT. When is it appropriate to use one over the other and is WVD used in real-time ...
malik12's user avatar
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How to detect "buzz" components in audio by frequency domain analysis

I am trying to detect the amplitude, frequency and phase of the dominant "buzz" in an audio signal. By "buzz" I mean a periodic signal with sharp edges. For example, an impulse ...
paperjam's user avatar
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1 vote
1 answer
148 views

Spectrum analyzer with multirate filter bank

This paper gives a spectrum analyzer using the multirate filter bank technique. The basic idea of the paper is that STFT can be interpretated as a uniform DFT filter bank. But the baseband filter of ...
ecook's user avatar
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1 vote
0 answers
375 views

How to plot the STFT of a .wav file in GNU Octave?

I'm quite new to signal processing and am trying to find the short time fourier transform of an audio sample and plot it (I believe the best way is as a spectogram?) using Octave (similar to this ...
user65457's user avatar
2 votes
1 answer
655 views

Choice of relationship between n_fft and window_length in STFT

Not a veteran in Signal Processing, it would be extremely appreciated to help me understand the idea/heuristic behinde the idea in STFT that $$\text{nfft} \ge \text{window length}$$ At least from a ...
LambdaDelta34's user avatar
3 votes
2 answers
352 views

What is the cause of STFT artifacts when different signals overlap?

I'm trying to learn about why signals that cross in an STFT cause apparent artifacts in the magnitude. I've been looking at the example below, written in python, where a gaussian peak overlaps with a ...
mgpanas's user avatar
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1 vote
0 answers
78 views

STFT for Classification

I am working on this project in which I am using Short Time Fourier Transform (STFT) for feature extraction before applying classification model. I have a time series sensor data, applied signal ...
Aisha Nasir's user avatar
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1 answer
292 views

Why does varying n_fft change the range of x axis values when plotting STFT?

I am using librosa.stft to apply an STFT to an audio sample and display a spectogram of the results when using different sampling windows (...
John Harrington's user avatar
2 votes
1 answer
235 views

Why does NMF (Non Negative Matrix Factorization) decompose a spectrogram into time and frequency component?

I compute the NMF over a spectrogram (magnitude of STFT of a signal) in this way: W,H = NMF(MyStft,r) # where r=2 is the rank W and H respectively contain the ...
Rebecca's user avatar
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1 answer
64 views

Spectrogram of a shock event

I have measured data of a vibration with chirp input were I suspect unwanted shock events occurred. I therefore thought about computing the spectrogram of my time histories to check the frequency ...
Rhei's user avatar
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1 vote
1 answer
75 views

Filterbank Interpretation of Inverse STFT With Hop

The slide below, borrowed from CMU, shows the typical interpretation of the "filterbank interpretation" of signal reconstruction from a Short Time Fourier Transform. As far as I can tell, ...
Novak's user avatar
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4 votes
2 answers
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How to calculate short-time fourier transform (STFT) when the window length is greater or smaller than the FFT size?

I have been trying to understand the weighted overlap-add (WOLA) method. By searching papers and posts in dsp.SE, I found that the window length can be larger and smaller than the FFT size. 1. Window ...
ecook's user avatar
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1 vote
0 answers
209 views

How to create overlapping frames of input signal for stft using HDL coder for FPGA implementation?

I want to implement stft on FPGA. For this purpose I use HDL coder and the problem is I have no idea how to create overlapping frames of data for further FFT. In my example I want to use 256 frame ...
Yegor Krapovnitskyi's user avatar
0 votes
2 answers
261 views

Impact of STFT window function and FFT length on computation time

I have been doing a study which part of it includes a comparison of computation time vs window type and length (among some other things in the computation time, however I speak in terms of relative ...
rshah's user avatar
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0 votes
1 answer
159 views

Best way to get the bin amplitudes of an audio DFT "normalized" 0-1

I'm working on a spectral processing plugin that's predicated on allowing the user to manipulate per-bin values in an STFT algorithm. I normalize the bin amplitudes by diving them by $N$ (number of ...
Jackson Kaplan's user avatar
2 votes
1 answer
332 views

Performing STFT after Butterworth Filter Seems Lower in Resolution

I have a signal recorded at 2MHz sampling rate. Before any decimation might be required, I first looked for peaks in my periodic recorded signal using STFT/spectrogram. From here, I can clearly see ...
rshah's user avatar
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0 votes
1 answer
360 views

Calculating Short Time Fourier Transform Manually

I am doing a project on short time Fourier transform, I have to perform STFT for 128 data points. I have developed a Matlab code to perform the STFT operation. But, my main concern is, I need to ...
radium88's user avatar
1 vote
1 answer
202 views

Classifying STFT from multiple signal samples

I have a collection of signals (IQ wav) split up into ~2s samples of sampling rate 2MHz, and can collect the STFT information from these samples through the following code: ...
rshah's user avatar
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