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Questions tagged [stft]

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1answer
26 views

Music source separation: Incomplete notation in published IS-NMF/EM pseudo-algorithm?

In a paper by Fevotte et al. on IS-NMF, which describes algorithms/implementation for multiplicative and EM variants of IS-NMF, the following algorithm is provided for IS-NMF/EM: In the algorithm's ...
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0answers
42 views

IFFT during ISTFT - and Nyquist

Using a compilable programming language (not Librosa, Matlab, etc), I am attempting to perform ISTFT on filtered (masked) source STFT matrices obtained from NMF. During the original construction of ...
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2answers
47 views

STFT window width vs. detectable Hz range

Assuming 44100 samples per second in a short 4-8 second-long audio .wav file, if I want perform FFT to detect the power spectrum, amplitude, and phase shift from 20 Hz to 10000 Hz (humans lose the ...
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1answer
39 views

Feature Extraction of Insect Sounds

First of all, forgive me if I sound stupid. I am still learning Audio Processing. So I am trying to make a machine learning model for detecting a specific insect through sound. Here is a sample raw ...
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0answers
20 views

Modified STFT resynthesis

This post is basically a follow-up to my recent question, which I asked here How to deal with phase incoherence issues after manipulating a signal in the frequency domain? In short, I'm modifying the ...
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0answers
36 views

How to deal with phase incoherence issues after manipulating a signal in the frequency domain?

Let's say that we want to manipulate a signal in the frequency domain using a short time Fourier transform and once we're done , we use an inverse STFT (plus overlap and save) to convert the results ...
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0answers
16 views

Is it possible to restore audio that has been tonally modified by a phase vocoder?

My objective is to apply some process to the modified audio that allows me to obtain the original audio. I think it can be solved through machine learning techniques. I don't know if there is any ...
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1answer
50 views

Power Spectral Density of Finite Signals

I have a basic confusion which I hope someone can help clear. Say I have two signals: $S_1=\sin(2\pi t) \forall t\in[0,+\infty]$ $S_2=\sin(2\pi t) \forall t\in[2,5]$, $S_2=0$ otherwise Now let's ...
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1answer
89 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 ...
2
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2answers
82 views

STFT on time varying signal with good time and frequency resolution

I am trying to determine the main frequency of a noisy signal that varies in frequency over time. Ideally I want to detect changes in the frequency as rapidly as possible - say 50Hz update rate, but I ...
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0answers
16 views

Estimate peak bandwidth from adjacent STFT bins for notch filter

I am using STFT to extract a strong, frequency varying signal from a continuous set of digital samples. I am able to do this very successfully and am determining the peak bin using PSD and 50% overlap ...
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2answers
96 views

Old style signal processing?

I am wondering if "an array of overlapping band-pass filters" it is 'mostly' equivalent to a Short-Time Fourier transform. See this (figure down), where $s(t)$ is the signal; LPF a second-order low-...
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1answer
44 views

Implementing MVDR beamformer in the STFT domain

I am trying to implement an MVDR beamformer for the first time. I was reading a couple of papers and books with many different notations and I am a bit confused. In my case, without loss of ...
1
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2answers
81 views

Multi Resolution STFT for audio

I am looking at trying to achieve a multi resolution STFT analysis on a log sine sweep audio measurement. I have an impulse, and I would like to perform two different windowed length FFTs on the ...
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1answer
54 views

STFT output frequency does not match sin wave frequency

I have the following function and pre definition for producing a sin and its' stft: ...
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1answer
59 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 ...
0
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1answer
107 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 ...
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3answers
311 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?
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0answers
28 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 ...
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0answers
76 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. ...
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0answers
17 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(...
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0answers
205 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 ...
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1answer
106 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 ...
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1answer
30 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 ...
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1answer
62 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
215 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 \|...
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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 ...
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0answers
23 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
92 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} ...
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0answers
55 views

Scipy stft, how is shape of f determined?

Using scipy stft, like this : ...
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0answers
87 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
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1answer
135 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 ...
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1answer
58 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
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1answer
139 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 ...
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2answers
497 views

How to calculate the PSD from the complex calculated STFT?

I have calculated the STFT with scipy python library: ...
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0answers
80 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
190 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?
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1answer
162 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 ...
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0answers
92 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
254 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
73 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, ...
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0answers
50 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
129 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
47 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
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1answer
692 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 ...
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3answers
549 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 ...
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1answer
216 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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1answer
45 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
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1answer
2k 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
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1answer
147 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. ...