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Questions tagged [stft]

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0
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1answer
8 views

Spectrogram Time Resolution with Overlap

I understand that the time resolution of a spectrogram with no overlap is the sampling frequency divided by the window length. How does this change with, say, 50% overlap? Does this double the time ...
3
votes
3answers
282 views

Does it make sense to use a wavelet that is equal to a sine of one period?

Would I get same results with STFT method (short-time Fourier transform) if I try this?
1
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0answers
24 views

When do phases not exist for spectrograms?

I have been reading a paper on the "Single pass spectrogram inversion" and I came across this in the Introduction part. In many applications, the analysis and modification of the Short-Time ...
1
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0answers
18 views

How to express STFT and ISTFT as a 1d convolution and 1d deconvolution in tensorflow/keras

I'm trying to implement this paper in tensorflow and keras. At the end of section 3 it says. ...
0
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0answers
14 views

Derivation of the reassigned STFT magnitude of a complex exponential

I have a complex exponential defined as $x(t)=Ae^{i2\pi f_{0}t}$ and its short time Fourier transform with respect to the analysis window, $g(t)$ is defined as, $$X_{g}(b,f) = \int_\mathbb{R} x(t+b)g(...
0
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0answers
17 views

Frequency range for STFT in Librosa

I am currently looking at the STFT for Librosa. I was wondering how to understand the output of the STFT function, specifically what kind of frequencies the different values represent. Say I have a ...
-1
votes
1answer
38 views

Spectrogram power/magnitude normalization in analogy with image intensity normalization

In analogy with the 8-bit grayscale image color depth, in which the intensity of a sample pixel is normalized to a value between 0 and 255 by taking into account the minimum and maximum intensities ...
0
votes
1answer
13 views

How to pad a array representing music to pad the stft of this array?

I have an array named samples of size (2, 1321967) representing an audio file. When I pass it to scipy stft with ...
0
votes
1answer
38 views

How to deal with overlap in STFT when considering the highest energy among multiple channels

I have a 4 channels audio file. As a pre-processing step, it goes through an STFT with $T$ frames and $M$ frequencies. The output is divided into magnitude and phase per channel, so for $C$ channels, ...
3
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2answers
171 views

STFT calculation with Gaussian Window

$$ f(t)=\exp(jat^2) \,\,\, and \,\,\, g(t)\,\,is\,\, a\,\, Gaussian\,\, Window:$$ $$ g(t)= \left (πσ^2\right)^{\frac{-1}{4}}\exp\left (\frac{-t^2}{2σ^2} \right ) , \,\,\,\,\,\,\left \|g(t) \right \|...
1
vote
0answers
16 views

Bandpass filtering with passband changing with time

Is it possible to implement some sort of filter which adapts as a function of time? Specifically, say I have a "noiseless" model of some signal which has the same frequency components at the same ...
0
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0answers
16 views

Criteria for Inverse STFT

So far I have studied the STFT and how it works. Following this question: Inverse Short Time Fourier Transform algorithm described in words , I got a grasp of how it works and how to implement it. ...
2
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1answer
80 views

Frequency estimation on chaotic waveform

The target signal is generated by the following analytically solvable hybrid chaotic oscillator \begin{equation}\label{eq:1} \ddot{u} - 2\beta \dot{u} +(\omega^2+\beta^2)(u-s)=0 \end{equation} ...
0
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0answers
34 views

Scipy stft, how is shape of f determined?

Using scipy stft, like this : ...
0
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0answers
42 views

Find fundamental frequency in short time Fourier Transform

In an implementation of phase vocoder using Python, I found the author get an approximation of the fundamental frequency of STFT using the following formula: Freq0 = B/A * abs(B/A) where B is the ...
2
votes
1answer
75 views

How to set STFT-parameters to visualize woodpecker / Sawtooth Signal? ​

I always wanted to work with FFTs and Spectrograms to characterise sounds and their frequencies using python. Lately I recorded a woodpecker at his work. Woodpecker Wav File To know where to look ...
0
votes
1answer
38 views

How to classify the movement type of a target into two categories(direct motion or else) by using a doppler radar?

How to classify the movement type of a target just into two categories(one is direct motion which is almost straight line movement and the other is anything else) by using a doppler radar with a ...
2
votes
1answer
61 views

How to reduce synthesis artifacts produced by phase vocoder?

I implemented the phase vocoder algorithm in Python to time-stretch speech signals by following this paper and referring to this MATLAB tutorial. I can distinguish words in the original signal from ...
0
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2answers
206 views

How to calculate the PSD from the complex calculated STFT?

I have calculated the STFT with scipy python library: ...
0
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0answers
55 views

How to know the time of my window to calculate the STFT with python knowing only the length?

I am trying to implement a work presented in an IEEE paper where they have mentioned that the STFT was performed on the signal measurements to obtain a spectrogram with no overlap window of 3 min : I ...
3
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1answer
77 views

Wavelet Transform and STFT

How wavelet transform is different from STFT. I'm not able to understand what is resolution in frequency domain means?
0
votes
1answer
103 views

How to calculate STFT of a function for a rectangular window

How to calculate the STFT (by hand) of $$u(n)\cos(0.2\pi n)$$ for a rectangular window of a length 20, positioned at $n = 5$. I know that to use STFT I need to divide longer signal to a shorter parts ...
1
vote
0answers
71 views

How to estimate noise by eigendecomposition of the variance covariance matrix?

I'm new here so I will try to be as clear as possible. I am trying to apply some techniques from signal processing framework to denoise financial time series. I would like to know if what I am ...
2
votes
2answers
203 views

Other time-frequency-plane tiling than STFT, DWT, ConstantQ-Transform: multiresolution STFT?

It is known that a) the STFT gives a rectangular tiling of the time-frequency plane b) the Wavelet transform gives a non-linear tiling (better frequency resolution for low-frequencies, and better ...
1
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0answers
52 views

Can Reassigned-STFT be an invertible transform? Algorithm for “Signal => Reassigned-STFT => masking => Reassigned-ISTFT => Output signal”

It is well known in DSP that this is a successful method to modify audio signals: Signal => STFT => masking => ISTFT => Output signal For example, ...
1
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0answers
44 views

Efficient audio power spectrum estimation

I am working on a small personal project where I want to control a matrix of roughly 100 actuators with an audio stream. The goal would be that the user can see/feel the music features in the movement ...
2
votes
1answer
119 views

Separate two sinusoids with very close frequencies (5 Hz difference) in a 44.1 Khz audio signal, with good time-domain resolution [closed]

Here is an audio signal which is a mix of (WAV file available here): a 2000 Hz sinusoid, beginning at 1.00 sec, without fade-in/fade-out a 2005 Hz sinusoid, beginning at 1.031 sec, with a slow fade-...
0
votes
1answer
43 views

Analyzing audio by looking at its time-frequency points in real- imaginary plane

I am performing Short-time Fourier transform on an audio signal (I dont know how to attach the audio file here). The sound was recorded in anechoic chamber and the source is supposed to come from left....
0
votes
1answer
434 views

How do I apply a binary mask and STFT to produce an audio file?

So here's the idea: you can generate a spectrogram from an audio file using shorttime Fourier transform (stft). Then some people have generated something called a "binary mask" to generate different ...
1
vote
3answers
387 views

Denoising a signal

I'm starting hydraulic experiments, where I'd have to measure velocity in an unsteady flow with a device called Acoustic Doppler Velocimeter. In DSP terms, I'd have a nonstationary signal in a shape ...
0
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1answer
164 views

1D signal to 2D spectrogram

I struggling at transforming a 1D breathing signal into 2D spectrograms, power spectral density as a function of time and frequency. Does anyone have an idea about that?
0
votes
1answer
41 views

How to Calculate the number of DFTs taken in a STFT

Given variables of window size (W), overlap (O), and length of the Signal (S) (in my case, length of a song) and I am trying to determine an equation that gives me the number of DFTs that would be ...
2
votes
1answer
1k views

STFT amplitude normalization, librosa library

So librosa.core.stft returns a complex single sided spectrogram. My question is: What normalization of the amplitude values should I perform afterwards? I believe I have to multiply the amplitude ...
1
vote
1answer
120 views

CMV: COLA constraint is not necessary

In the literature on the short-time Fourier transform (STFT) it is often stated or implied that the constant overlap-add (COLA) constraint must be satisfied in order for the STFT to be invertible. ...
0
votes
1answer
127 views

Add noise/signal to mel log spectrogram

I have a predicted mel log spectrogram $S$ and I want to add a noise signal $\eta$ to it. S = log(mel-filterbank(abs/real part of(stft(signal))) The naive way ...
0
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0answers
185 views

output shape of STFT

I cant figure out why our output image is 257 * 32 , 32 I know why , but 257 I cant understand ? this is the exact word of this paper wich applied STFT on 3 channel of eeg signal : Short time Fourier ...
0
votes
1answer
78 views

Some doubts in the matlab code of computing Wigner distribution

I found that a discrete form of the Wigner distribution was $$WD(n,k) = \sum_{m = -N/2}^{N/2}f(n+m)f^*(n-m)e^{-j\frac{2\pi}{N+1}2mk}$$ where $f(n)$ is the signal and time limited within $|n|\le N/2$. ...
2
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0answers
157 views

Reconstruct signal from its Spectrogram only

The spectrogram of a signal throws away the phase information, but it is said to be possible to reconstruct the signal only from the spectrogram [1] via $$s(t) = \frac{1}{2\pi s^*(0)}\int_{-\infty}^{\...
2
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0answers
66 views

Selection of transforms, windows, wavelets for current signal analysis

I am new to this topic but I already read about the propperties of different signal analysis methods. I am stuck with the obvious advantages of FFT, STFT and Wavelet transforms but can't find good ...
1
vote
3answers
2k views

Window period(overlap) and FFT

How does changing the window period (i.e the number of points overlap between two frames) affect the FFT results ? Suppose that a time series signal was converted to frequency domain by FFT with ...
-1
votes
2answers
730 views

STFT computation

I'm trying to compute the STFT by my self. Thus, I wrote the following code: ...
4
votes
1answer
759 views

Is it possible to recover a waveform from spectrograms of magnitude *and* phase?

It is my rough understanding that a typical spectrogram discards phase information by squaring only the real-valued part (magnitude) of the STFT (I know it's not quite this simple, but feel free to ...
0
votes
2answers
107 views

What's a good physical description of the following matlab code?

I've inherited some matlab code and I can't really understand what the resultant signal really means. The input is audio and the code first performs an STFT/spectrogram (sliding window FFT of size ...
0
votes
1answer
513 views

Inverse Fast Fourier with overlap

I had to work with sound(denoising algorithms), when I read about an algorithm it said that we do DTSTFT(Discrete-time short-time fourier transform) we will create an overlap between each "chunk" of ...
5
votes
1answer
144 views

In the formula for the windowed Fourier transform, why is the complex-exponential term not time-shifted to the position of the window?

I have a question about the "windowed / short-time / short-term" Fourier transform that is somewhat perplexing me. I have now added an Addendum at the bottom, where the issue is presented more ...
0
votes
1answer
167 views

Why are analytic signals so important in Time-frequency analysis?

I am little confused about why we need analytic signals so bad in time-frequency analysis. What might happen if I use non-analytic signals to do time-frequency analysis?
0
votes
1answer
723 views

How to convert dB back to manitude and then to rectangular format [duplicate]

I am experimenting with audio (wav files) using Short-Time Fourier Transform (STFT) in Python using scipy.signal.stft. As I ...
2
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0answers
491 views

Executing a command based on a Short-Time Fourier Transform Output

I am currently calculating a Short-Time Fourier Transform (STFT) in Python using scipy.signal.stft. I am producing the image of the STFT shown below in real-time, ...
0
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0answers
239 views

Hilbert Spectrum vs. STFT

If I wanted to plot a spectrogram of a signal, I would by default use the Short Time Fourier Transform. However, the Hilbert transform does something similar: it lets us calculate instantaneous ...
2
votes
3answers
275 views

Is “Windowed Fourier Transform” a synonym for “STFT”?

Sometimes I find the notation WFT (Windowed Fourier Transform) while other times I see STFT (Short Time Fourier Transform). Are they the same?