# Questions tagged [short-time-ft]

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### How to calculate FMCW Radar Chirp STFT?

I have received signal from FMCW Radar which is of the shape [128x64] = [Number of samples per chirp x Number of chirps per cycle] and i want to calculate the stft i am calculating it with stft ...
27 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 ...
27 views

### Length of Hamming Window to Resolve a Harmonic

I am trying to answer the question: "Given a single-sourced pitch signal with a fundamental frequency of 440Hz and a sampling rate of 44100Hz how long should the Hamming window of the STFT analysis ...
20 views

### STFT of ISTFT in the Griffin Lim Algorithm

The Griffin-Lim algorithm for phase recovery (based on the magnitude of an STFT) involves a step that is: STFT(Inverse STFT(...)). This seems to be the key iteration in the algorithm. This Quora ...
103 views

### How to derive the bin width / maximum frequency of DFT/STFT

The bin width is given by the $F_s / N$ and the maximum frequency is given by $F_s / 2$ where $F_s$ is the sample rate and $N$ is the number of samples of the DFT. Going between these is trivial, but ...
64 views

In the Short-time Fourier transform what are the tradeoffs between different: window functions window lengths sample rates
60 views

### What's wrong with my STFT implementation?

I'm studying the linear convolution for achieve more complex results in Audio FX. My main goal is to implement a realtime convolution between two stream of sound in live perfomance (for example Sound ...
31 views

### STFT Reconstruction After Modification

Why do we want to minimize the difference between the two signals the original one and the modified one when all we want is the modified constructed signal? What is the purpose of making it the ...
28 views

### Short Time Discrete Fourier Transform to detect time dependent changes in a frequency of interest & Filter

I am working in matlab to compute the fourier relative phase of two signals as per https://sci-hub.tw/10.1123/jab.2017-0250 I have identified the fundamental frequency ($f_1$) for the signals (1.7 Hz)...
53 views

### How to generate a sinusoid with STFT at a frequency which is between bins

Is it possible to generate a sinusoid at a frequency which is between two bins (so a fractional index) with the STFT algorithm (by filling bins and doing the inverse) ? If yes then how can this be ...
42 views

### Why should one choose the maximum as reference for power-to-decibel conversion?

I have seen that one converts the amplitude to decibels through: $\text{dB(S)}=10 \text{log}_{10} \big(\text{S/ref}\big)$, where $\text{S}$ is the output of a STFT and ref the reference value for the ...
61 views

### Why is the number of frequencies decomposed in scipy.signal.stft() equal to the hop size?

I asked this over on StackOverflow first but figured you fine people might know more about signal processing (duh). I'm trying to calculate the spectrogram of an audio file in python. There's a nice ...
38 views

### What is the value range of log magnitude spectrograms?

I'm quite new to this field and have a probably rather basic question: Is there an upper bound for the values in a log-magnitude spectrogram generated like this: ...
78 views

### Advantage of applying a Window Function in Analysis and Synthesis of STFT?

I'm studying Short-time Fourier Transform and I learned that if you apply a windowing other than rectangular, you need to overlap the frames---for example, 50% overlap for Hamming family---to ...
39 views

### Synthesis of 75% Window Overlap Add method for Short-Time Fourier Transform (STFT)

I'm doing the overlap-add method for STFT and I quite understand the implementation if it's a 50% overlap (where I add the 2nd half of the previous frame to the 1st half of the current frame during ...
32 views

### Volume increase of a magnitude spectrogram

Let's say I have an audio waveform and I perform an STFT on the waveform and then take the absolute value to get the magnitude spectrogram. Is there a transformation that I can make to that ...
30 views

### Cannot reconstruct constant overlap add STFT perfectly

I am implementing an STFT function for spectrogram of certain audio files. Here's my function: ...
29 views

### How to create different Time frequency images from a data

I'm new to Python. I have a time series in a CSV file that has about 5000 rows and 3 columns. I have split the data into training and testing in ratio 70:30 respectively. However, I have a problem ...
48 views

### Given 1 recording of my voice, how can I process it to sound like 2 independent recordings of my voice played in unison?

I have one recording of my voice $x[n]$ singing a song. One thing I could do is independently record me singing the song again to obtain $y[n]$. Then, $z[n] = \frac{1}{2}\left(x[n] + y[n]\right)$ ...
46 views

### Mixing signal with noise in frequency space (STFT)

I am working on a preprocessing function which is supposed to mix two audio signals clean and noise in the context of neural ...
36 views

### Invertibility of Time-Dependent Fourier Transform

I am reading Oppenheim & Schafer's (O&S) Discrete Time Signal Processing (2nd or 3rd edition, does not matter) and I find hard to understand a technicality behind the Time-Dependent Fourier ...
51 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: ...
49 views

### Clustering real and imaginary values within a frequency row of an STFT

I am analyzing a short audio .wav file of a drum and piano for source separation. (not using interpretable languages like Librosa, Scikit, Matlab, or R, but rather a compilable language in .NET). ...
83 views

### extracting mfccs after beamforming

I have a deep network for sound classification with mfccs as features. I wish to go through the process of beamforming before applying the classification. The original network uses ...
38 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 ...
48 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 ...
75 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 ...
61 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 ...
32 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 ...
46 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 ...
19 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 ...
101 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 ...
108 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 ...
121 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 ...
18 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 ...
106 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-...
85 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 ...
163 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 ...
69 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: ...
86 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 ...
224 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 ...
326 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?
34 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 ...
132 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. ...
385 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 ...
286 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 ...
41 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 ...
110 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, ...
$$f(t)=\exp(jat^2) \,\,\, and \,\,\, g(t)\,\,is\,\, a\,\, Gaussian\,\, Window:$$  g(t)= \left (πσ^2\right)^{\frac{-1}{4}}\exp\left (\frac{-t^2}{2σ^2} \right ) , \,\,\,\,\,\,\left \|g(t) \right \|...