Questions tagged [stft]

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1answer
13 views

The effect of doubling the sample rate in Spectrogram

If we have an audio file and we only change the sample rate (double it), what changes our spectrogram will have (after using the stft)?
4
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3answers
130 views

Role of window length and overlap in uncertainty principle?

I am trying to predict epilepsy using spectrograms and a convolutional neural network. So far I have achieved a validation accuracy of 86% which i feel like is pretty good. Lots of the papers doing ...
1
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1answer
29 views

How to train a FCNN with Spectrogram images?

I'm working on a audio dereverberation deep learning model, based on the U-net architecture. The idea of my project came from image denoising with autoencoders. I feed the reverbered spectrogram to ...
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0answers
20 views

Spectrogram normalizaion to train a Fully Convolutional Model for Audio dereverberation

I'm trying to implement a deep learning based dereverberation algorithm. The network I am using is inspired by the U-net. The idea is to supply the reverberated spectrogram as input and 'clean' it ...
8
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2answers
569 views

Advantage of STFT over wavelet transform

I have learned about STFT and wavelet transform recently, and wavelet transform seems better than STFT in my opinion. So, I wonder if there is any advantage of using STFT than WT, and if so, what are ...
2
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1answer
51 views

Understanding stability in frame theory. Wavelets

I'm trying to grasp some understanding of the concept of stability in the context of the frame theory. The definition of frame in ref1 states that a sequence of functions $\{ \phi_n \}_{n \in \Gamma}$ ...
1
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1answer
28 views

Hop size in STFT

I am reading the documentation of scipy.signal.stft function: https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.stft.html#scipy.signal.stft. My question: is the 'noverlap' parameter of ...
2
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1answer
73 views

Window with optimal sidelobes for a given ENBW / frequency-resolution

Is there a family of windows which is "optimal" in terms of energy above/below a boundary, but with controllable ENBW/bandwidth? By optimal, I mean maximising energy concentration inside ...
1
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1answer
44 views

Should i use window with hop_size in Wavelet Transform or Discrete Wavelet Transform?

I have a signal (audio - voice) with 1 second of duration with sample rate of 50000 Hz. It is big signal and I wish extract some features and apply pattern recognition or classification. My question ...
0
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1answer
85 views

How to specify parameters in scipy.stft to reproduce published analysis

I am starting a project on this Keggle dataset containing EEG registrations (sampled at 128 Hz) of several subjects. What I am really interested in is the final ...
1
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2answers
83 views

How to objectively measure how "good" a time-frequency representation of music is?

I've been studying the time-frequency uncertainty principle of Dennis Gabor, and the tradeoff of the STFT window size in representing the tonal and transient characteristics of the musical signal ...
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0answers
44 views

Mapping STFT magnitude to sound intensity level

I have a signal for which I have computed my STFT magnitude spectrum in dB. The plot is the following: This is my magnitude spectrum in dB computed with ...
2
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3answers
176 views

scipy.signal.spectrogram() - how to handle gaps in the timeseries data

Looking at the magnitude of variable stars - the dataset is from here: https://dogwood.physics.mcmaster.ca/Cepheid/URL/MW/BD-10d4669.html The magnitude plot: ...
0
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1answer
137 views

scipy.signal.spectrogram() with noverlap=nperseg-1, what are the possible side-effects?

I'm using a simulated data set which can be downloaded from the link in the fist paragraph on this page (it's an Excel file): https://www.analyticbridge.datasciencecentral.com/forum/topics/challenge-...
0
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1answer
49 views

scipy.signal.stft temporal resolution

Using the STFT function from scipy.signal has produced unexpected results for me. I am performing an STFT on 10 seconds of data, sampled at 25,000 Hz. I am using STFT settings of nperseg=256 and ...
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0answers
77 views

Wrong amplitude in the FFT for 10 seconds measured signal

I measured a signal with the Osziliscope that I generated with a signal generator. The signal is a pure sine wave with a frequency of 1 kHz and a peak amplitude of 2.5 V, I measured the signal for ...
1
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2answers
195 views

What is the advantage of overlapping windows while evaluating Spectrogram?

I've seen many documents that refer to calculate spectrogram through overlapping windows but haven't found clear documents on why this is done and how to calculate the number of points that need to be ...
0
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3answers
62 views

Why Matlab Spectrogram of slow and rarely sampled signal shows high frequencies

I have a signal, which was measured for 14.4 minutes (= 864 seconds). There are 192 measurements, so one measurement was done in every 4.5 seconds, which results in a 0.22 Hz sampling frequency if I ...
2
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1answer
90 views

Biorthogonal Windows

I am starting to study about the concept of biorthogonal windows and the relation to (Discrete) Fourier transform and short-time Fourier transform (STFT). I have not found an introductionary review of ...
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3answers
72 views

How Short-time Fourier transform (STFT) is different from from filtering?

If we want to know frequencies in a signal over time I know we can use Short-time Fourier transform (STFT). but I read in a paper "The spectrogram representation was obtained by first filtering ...
1
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2answers
120 views

STFT with varying window lengths (like the continuous wavelet transform)

I was wondering if it is possible to use windows of varying lengths when making a spectrogram based on the short-time Fourier transform (STFT). That is, for higher frequencies I would use shorter ...
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0answers
35 views

Mathematically expressing FFT and STFT on a matrix

I have a matrix $q(m,n)$, where $m$ represents the vertical direction and $n$ is the horizontal direction. I need to perform the following three operations: take FFT of matrix $q$ in the vertical ...
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3answers
588 views

What is really the Mel-filterbank?

After applying STFT to a signal, you typically need to convert the frequencies to the Mel scale. Typically the frequency values range from $0$ to $N/2$, where $N$ is the width of each sliding window. ...
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0answers
25 views

How to determine STFT parameters as a function of desired resolution

None of the Q&As I've seen thus far have given a clear answer to what seems like a simple question: assuming I know the CenterFrequency, ...
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0answers
101 views

What is the unit of the color axis on a Matlab spectrogram, and bandpower?

I am new to signal processing, but successfully made a spectrogram with Matlab. It is nice and working, showing the expected output on the graph, but I just cannot understand what the numbers mean on ...
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0answers
50 views

Short Time Fourier Transform has different frequencies than Fourier Transform?

The reason we do the STFT is so that we can analyse for short segments of time how much of the components in the frequencies of the FT are present. However, it may be possible that completely ...
3
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2answers
149 views

Why does Matlab spectrogram look stripy when windowed input is zero-padded?

I am working on a little project, and stumpled upon something I cannot understand yet. I am learning cognitive science, and don't have DSP knowledge background, only learning from what I find on the ...
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0answers
48 views

Efficient STFT computation

I am calculating the STFT using scipy, and then reducing it in size, flattening and then normalising it. Code is below. It's incredibly slow, given I'm trying to ...
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1answer
157 views

Using STFT as an input to a Neural Net

I'm trying to use the STFT as an input to a neural network. After flattening, there are over 4,000 features for a few seconds of audio. Is there a recommended way of summarising these to be a more ...
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0answers
68 views

STFT(Short-Time Fourier Transform) & DFT(or FFT) in Matlab

I want to try STFT & FFT using Matlab. What I wonder is STFT of signal computes the result that FFT(DFT) of each windowed signal and I can see the change of each frequency value over time. If I ...
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0answers
41 views

Audio-Processing for DeepSpeech model

I try to understand audio signal processing from Deep Speech: Scaling up end-to-end speech recognition paper. Quote: Since the Switchboard and Fisher corpora are distributed at a sample rate of 8kHz, ...
0
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1answer
25 views

Coherence for order spectra

The scipy signal coherence function computes for two time series the coherence as a function of the frequency. For rotating systems however, it is sometimes meaningful to analyze the two recorded ...
2
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1answer
47 views

Spectrogram without using stft

Can I use any kind of transform to make spectrogram, not just stft? Is it possible to get the spectrograms of a signal without using stft? What difference does it make if I calculate the frequency ...
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2answers
37 views

Stft of sinusoids

I have a sinusoidal signal of 10 minutes. For the first 5 minutes, the signal has a frequency of 100 Hz and for the next 5 minutes, the signal has a frequency of 200 Hz. 1 - If I look at the ...
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0answers
33 views

Filter length (N) has no effect on the reconstructed signal & Toeplitz Matrix

Hello Signal Processing community, I implemented a filtering algorithm called Minimal Mean Squared Error in Frequency domain with N-coefficient and Signal Detection (FMSENSD) in MATLAB, I got some ...
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0answers
113 views

The difference between tensorflow stft and scipy stft

I'm trying to wrap my head around stft, and checking the docs, tf.signal.stft and ...
2
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2answers
129 views

Synchrosqueezed STFT phase transform

Synchrosqueezed STFT paper, Synchrosqueezing based Recovery of Instantaneous Frequency from Nonuniform Samples, defines STFT phase transform as: $$ w(u, \xi) = \xi - \frac{\partial_tS_{g}f(u, \xi)}{j2\...
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1answer
110 views

Do i need to remove mean in STFT when working on music audio?

i need to apply a STFT to some music audio files but i can't understand if i should remove the mean or not. I know that for stochastic signals that is a must and that sometimes also necessary for ...
0
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0answers
21 views

How to get the phase/angle from an Alglib complex variable

It is easy to get the magnitude using alglib.abscomplex function (https://radfiz.org.ua/files/temp/Lab1_16/alglib-3.4.0.csharp/csharp/manual.csharp.html#gs_stdfunctions), but I would like to know, how ...
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1answer
209 views

revert back to stft from abs and phase

I have the following code on python ...
1
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1answer
67 views

Is there any way to align temporally two signals in spectrogram?

I am keen to know that If I have two signals say : Farend_signal (y[n]) and Nearend_signal (x[n]) and x[n] also contains an echo of y[n] with some delay. Is there any technique to align these two ...
0
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1answer
109 views

Determining statistically the bandwidth of a signal from a spectrogram

My question is how to determine the parameters of a signal from a spectrogram statistically. The most important parameters that I am looking for are the lower and higher frequencies of the signal. I ...
1
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2answers
812 views

Difference between librosa.stft and scipy.signal.stft

I read the source code of librosa.stft and sicpy.signal.stft, and notice that the calculation results of STFT(short-time fourier transform) in these two libraries are quite different: In scipy.signal....
2
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2answers
136 views

What mother wavelet should be chosen as an alternative to the STFT?

The Short Time Fourier Transform (STFT) is used to identify time localized frequency content of a signal. The STFT operates by chunking an input signal into blocks and performing FFT on the block, and ...
1
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1answer
65 views

Where is the mother wavelet defined in the Fast Wavelet Transform?

Referring to the Fast Wavelet Transform, this transform is implemented as a QMF filter bank. This algorithm consists of high/low pass filtering and subsampling. However, a wavelet transform is ...
1
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1answer
29 views

Why are the Continuous Wavelet Transforms of the same signal drastically different?

I'm currently studying wavelets and am running into confusion with regards to CWT coefficients. Ideally, I want a CWT algorithm that produces outputs similar to that of a STFT - i.e. produces ...
1
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1answer
134 views

How does modulation frequency appear in the modulation spectra?

I'm trying to familiarise myself with the concept of modulation spectra that I met in this work. My main question appears in the title: how does the modulation frequency appear in the modulation ...
0
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1answer
160 views

Is there a FFT algorithm with the circular buffering?

I have an audio signal and i want to process it sequentially. Is there an algorithm which allows to modify the spectrum of a signal when i remove a part of signal and add the other one? For example, i ...
0
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1answer
36 views

Does speech volume affect frequencies?

I have created a little classifier that listens for certain keywords. Sometimes it will not react to a keyword, but if I shout the word, then the classifier will be able to pick it up. The classifier ...
1
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2answers
93 views

Change the melody of human speech using FFT and polynomial interpolation [closed]

I'm trying to do the following: Extract the melody of me asking a question (word "Hey?" recorded to wav) so I get a melody pattern that I can apply to any other recorded/synthesized speech (...

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