Questions tagged [stft]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
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 ...
0
votes
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
votes
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
vote
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 ...
0
votes
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 ...
1
vote
1answer
71 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
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
votes
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
votes
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 $\{ \phi_n \}_{n \in \Gamma}$ ...
0
votes
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 ...
2
votes
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 ...
3
votes
3answers
683 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?
0
votes
1answer
151 views

STFT to spectrogram

I would like to know whether I am correct in my understanding of going from STFT to a spectrogram. My goal is to convert a spectrogram back to a wav file. If I have my STFT: ...
5
votes
2answers
299 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 ...
1
vote
1answer
300 views

Variance of the Discrete Gabor Transform for practical implementation

When we design a discrete Gabor filter for a 1D signal, how do we determine the variance of the filter, depending on the time step of the signal? Is there any empirical theorem/result that we should ...
1
vote
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 ...
0
votes
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. ...
2
votes
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\...
0
votes
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
vote
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 ...
1
vote
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 ...
1
vote
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 ...
11
votes
4answers
4k views

What's the difference between the Gabor-Morlet wavelet transform and the constant-Q transform?

At a glance, the constant-Q fourier transform and the complex Gabor-Morlet wavelet transform seem the same. Both are time-frequency representations, based on constant-Q filters, windowed sinusoids, ...
0
votes
1answer
128 views

Selected bin oscilation in STFT

I am looking for a noisy signal using STFT. My window length is 128 and I am using 75% overlap. I am using a Hanning window before running the FFT process. I am using Quinn's 2nd estimator for ...
0
votes
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
votes
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: ...
1
vote
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 ...
0
votes
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-...
3
votes
1answer
6k views

Spectrogram, time vs frequency localization, and length of signal

So I'm having some trouble conceptually and am hoping somebody can clear something up for me. This is long and I apologize for that but I want to provide as much information as possible so that the ...
1
vote
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
votes
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
votes
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 ...
0
votes
1answer
225 views

Phase difference calculation between two wave files

I am doing comparison between two wave files, How to calculate phase difference between those files? Second wave is generated by making some changes in the first one .I have tried calculating phase ...
2
votes
2answers
183 views

CWT Disapointing Frequency Separation

I'm attempting to perform multi-resolution analysis via Continuous-Wavelet Transform (CWT) using Pywavelets. I've heard that CWT is supposed to be superior to STFT due to varying frequency content as ...
1
vote
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....
0
votes
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
vote
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 ...
0
votes
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 ...
0
votes
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, ...
0
votes
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 ...
1
vote
1answer
147 views

How do I set window length and shift length for computing STFT on Scipy?

Does nperseg=32, noverlap=16 mean the window length is 32mS with a shift of 16mS? Refer here for more details
1
vote
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
votes
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 ...
2
votes
4answers
1k 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?
0
votes
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 ...
0
votes
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 ...
0
votes
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, ...
4
votes
1answer
684 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
votes
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
votes
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 ...

1
2 3 4 5 6