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Questions tagged [stft]

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0
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2answers
55 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
21 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 ...
2
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1answer
32 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
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1answer
53 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
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0answers
49 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
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2answers
133 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 ...
0
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0answers
32 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
38 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
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1answer
108 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
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1answer
42 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
174 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
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3answers
181 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
123 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
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0answers
62 views

noise reduction using STFT

I am having a little trouble when doing the noise reduction by using noise gating technique. I am doing below steps: STFT the background noise with 2048 Hanning window. The Hanning window is shifted ...
0
votes
1answer
39 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 ...
1
vote
1answer
749 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
103 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
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0answers
54 views

Oscillator resynthesis with interpolated phase in sinusoidal model

I'm implementing a sinusoidal model based on the STFT of an input signal: Analysis occurs at evenly spaced hops of S samples; spectral peaks are tracked and the peaks of analysis frame m are matched ...
0
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1answer
79 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
91 views

PSD using short time fourier transform

I am trying to calculate power spectral density over frequency bands (eg. alpha beta, gamma etc.). To do so I have been asked to apply 512 point short-time Fourier transform with 1s long window and ...
0
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0answers
106 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
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1answer
56 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
136 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}^{\...
3
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0answers
63 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 ...
0
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3answers
863 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
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2answers
370 views

STFT computation

I'm trying to compute the STFT by my self. Thus, I wrote the following code: ...
4
votes
1answer
485 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
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2answers
96 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
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0answers
43 views

How can i find the time delay using spectrogram?

We observe that in the first plot we have a delayed signal and in the second one, his spectrogram. My question is how can i find the time delay using spectrogram. I understand that if i sum the colums ...
0
votes
1answer
323 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
127 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
114 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
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1answer
485 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 ...
1
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0answers
301 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
201 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
219 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?
1
vote
2answers
126 views

Windowed Fourier Transform

I need some help with applying the properties of Fourier Transform. We define the windowed Fourier Transform of $f \in L^2(R)$ as $$Sf(\mu,\xi)=\int_\mathbb{R}f(t)g(t-\mu)e^{-i\xi t}dt$$ Prove ...
0
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1answer
755 views

Phase vocoder, pitch shift in MATLAB and C

I'm trying to make a Phase Vocoder in MATLAB. But I'm stuck with the calculations on changing the pitch. I browsed loads of website and I simply do not understand what to do. Currently I have in my ...
0
votes
2answers
463 views

Which is the difference in between the different STFT implementations? (Overlap-shift with zero-padding, overlap-add, overlap-save, etc)

I'm trying to understand STFT overlapping, why segments are concatenated and what are the consequences of this. My implementation (from other questions and repositories found) of the STFT in Python ...
2
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4answers
408 views

How to interpret the effect of different windows in short time fourier transform?

There are many categories of windows, e.g., rectangular, Gaussian, and triangular. What are their effects on STFT?
2
votes
2answers
253 views

Combining spectrograms with different windows to getting arbitrary time and frequency resolution

Spectrograms convert an amplitude-time signal into a frequency-time signal using Short Time Fourier Transform (STFT). The window size L used in STFT is a design choice. As L increases, you get higher ...
0
votes
1answer
412 views

Welch spectrogram

I have been using scipy's spectrogram function (STFT) to compute a PSD spectrogram for a non-stationary signal. I provide X length window (with nperseg = X/10) each ...
0
votes
1answer
50 views

Gain error when performing STFT spectogram of increasing frequency signal

I'm performing a STFT of a sine wave in which the frequency increases (up-chirp signal) using python numpy.fft as shown in the following code: ...
0
votes
1answer
198 views

Can STFT (Short-time Fourier Transform ) be more useful than FFT for analyzing stationary signals under some circumstances?

the nature of STFT is to be applied on non-stationary signals. for stationary signals STFT and FFT sounds exactly same to me. However, I was wondering if STFT can lead to better results compared to ...
1
vote
4answers
224 views

What do I lose when I set overlap rate to a really high value in STFT

If I don't care about computational cost, is there any cons when I put overlap rate really high in STFT?
1
vote
0answers
175 views

What is the algorithmic latency of STFT processing?

I was reading this paper, and in section 3 I got a bit confused. It claims that the algorithmic latency is equal to synthesis frame length. If the overlap between two consecutive frames is 50%, the ...
2
votes
0answers
100 views

What is the correct way to do Short term Fourier transform and extract the phase information from local sections of a signal?

I took a triangular voltage signal and taking it's time derivative I obtained the current through a pure capacitor. Then I took different portion of voltage and current signals, took their Fourier ...
6
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2answers
896 views

Signal processing techniques for an accelerometer signal?

I am running some tests where I am recording accelerometer measurements. I am looking to use elements of signal processing on this signal, but I am unsure about where to begin, or what my approach ...
0
votes
3answers
328 views

Why is the first axis of STFT frequency bin

When taking the STFT of an audio signal, the first axis is the frequency bins by convention, and the second axis is how it elapses through time. Is there a reason?
0
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2answers
1k views

Understanding overlapping in STFT

I understand the concept of the STFT. In order to avoid spectral leakage, you use a Hann window that overlaps by 50%. However, the problem that I have, is that the example code online does not account ...