Questions tagged [window-functions]

In signal processing, a window function is a mathematical function that is zero-valued outside of some chosen interval.

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Speech Endpoints Detection using Explicit approach

The "Fundamentals of Speech Recognition" text by Rabiner, mentions three approaches for Speech (Endpoints) detection - Explicit, Implicit, and Hybrid approaches. I am studying the block ...
Anantha Krishnan's user avatar
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1 answer
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Why is there a tradeoff between simplicity of a window function and its ability to be adjustable and controllable?

While studying and applying different window functions in a project I am working on, I found that known windows (here is an example paper which cataloged numerous windows) suffer from 2 kinds of trade-...
RajaKrishnappa's user avatar
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Window function with no sidelobes

I found the Hann–Poisson window on Wikipedia. It has no sidelobe for $\alpha \ge 2$. I am interested to know more examples of such window function with no sidelobes and what they are useful for. I ...
anonymousRabbit's user avatar
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What are the *undesirable* effects of windowing in Fourier space?

My goal is to split a periodic signal into two (or more) signals. The first signal would contain the low-frequency information, and the later signals, the higher-frequency information. These signals ...
user572780's user avatar
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1 answer
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Taylor Window Algorithm

I am trying to find out the algorithm for taylor window function but i have looked everywhere and i dont see any proper algorithm. I read it is similar to Kaiser Window but thats all I know. Can ...
Shubham Kapoor's user avatar
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Why window functions can't have both narrow main lobe and low-level side lobes?

Why window functions can't have both narrow main lobe and low-level side lobes? i got a hint from my mentor that it's quite often expained in books about wavelets... I thought it could be associated ...
Alexander's user avatar
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What can be done, on top of windowing, that can reduce spectral leakage?

I am relatively new to DSP, and I am trying to create a spectral suite plugin using the IPlug2 library for creating vst plugins, and an FFT library I found on GitHub. So far, I can perform an FFT on a ...
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Welch method implementation not smooth

I have been trying to recreate the welch method implemented in scipy.signal by hand but my results don't look close enough in my opinion. How come the scipy.signal.welch method is displaying much ...
Flitschi's user avatar
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Calculating the main lobe width of Dirichlet kernel

The Dirichlet kernel of order $N$ is defined as: $$ D(\theta,N)=\frac{\sin(N\theta /2)}{\sin(\theta /2)} $$ We know that the main lobe widths between zero crossings is: $4\pi/N$ I was wondering if ...
Sammy Apsel's user avatar
2 votes
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FFT Window question - high resolution windows

So I am pretty familiar with FFTs and FFT windows. I know that in general there is a tradeoff between mainlobe width and sidelobe levels. However, I recently stumbled across this discussion, where ...
Colin Marcus's user avatar
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What window functions allow for controlling the location of nulls?

Window functions are commonly used to control spectral sidelobes. Typically there is a trade between supressing sidelobes, and maintaining the resolution of the mainlobe. A window with lower sidelobes ...
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Decreasing gibbs phenomenon with window functions multiplied in time domain

I know about using fitering(e.g. window filters that used in frequency domain), wavelets for decreasing or even full eliminating gibbs effect but don't really understand how we can use window ...
Alexander's user avatar
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How to adjust the length of the window of the Fourier transform with respect to the length of the signal in Python

I ran the following code in Python, setting the window length to 5s, but he reports an error as the window length does not match the signal length. How should I adjust it please? code: ...
BaiYueChu's user avatar
2 votes
1 answer
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Noise spectral density and windowing

I am wondering about the definition of Power Spectral Density, in the context of measuring noise, i.e., Johnson-Nyquist (thermal) noise. Usually a windowing method, like Welch's method, is used to ...
Nick's user avatar
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Power spectrum, Power spectrum density and windowing functions

At the moment I have some trouble understanding the different methods. I would like to calculate both the Power Spectrum and the Power Spectrum Density. As the name suggests I thought that $PSD = PS / ...
3dSpatialUser's user avatar
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1 answer
186 views

How Best to Characterise a Window Function

How do I characterise my window function? Do please forgive me here as I am more a practical than theoretical person. I have invented a window function which I use prior to discrete Fourier transforms....
Richard's user avatar
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Dropping the zeros at the edge of window functions

I have learned that Scipy's implementation of the Hann window allows receiving both a symmetric window, and a periodic window (meaning the last zero element is dropped). As far as I understand, the ...
Gideon Genadi Kogan's user avatar
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1 answer
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N-point DFT of window function

I am currently choosing a window function to analyze signals in frequency domain. While I understand the reasoning behind using a window function and what to look for concerning main lobe and side ...
Geralt von Riva's user avatar
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Kaiser window but desired frequency response extends beyond pi?

Passband : 0 to 0.5π Stopband : 0.7π to 2π Is there a way to reduce this to a 0 to π scale? If I had to guess, we should be able to simply divide the edge frequencies by 2 and use the time scaling ...
rjpj1998's user avatar
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Understanding FIR windows

We learnt about the various windowing techniques recently and I can't seem to wrap my head around why one would use anything other than a rectangular window. I created a signal with 10 evenly spaced ...
rjpj1998's user avatar
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Amplitude scaling of window functions for FFT

I need to perform an FFT on a signal sampled with 20 kHz and a measurement time of about 10 seconds. The signal contains frequencies of up to 2 kHz but I am mainly interested in the bandwidth of 0 to ...
Geralt von Riva's user avatar
1 vote
1 answer
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Effect of windowing on signals

I have an input signal of frequency 1000Hz. Sampling frequency=16kHz. I compute the FFT on 128 input samples and plot the magnitude spectrum. I am not doing the normalization by 128. My two sided ...
Deepa's user avatar
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Proof for the energy correction factor of DFT

I am looking for a mathematical proof for the energy correction factor in conteext of windowed discrete fourier transform. In Spectrum and spectral density estimation by the Discrete Fourier transform ...
mocquin's user avatar
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3 votes
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How to understand "independent sample rate" of windows?

A window metric called independent sample rate is given in a book that I recently read. It says that in spectral estimation, the variance of power-level estimates is inversely proportional to the ...
ecook's user avatar
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What is the necessity of shifting the impulse response of a filter to the front of the time domain buffer and windowing?

I was reading the answer to this question provided by Phil Karn. In the answer, it has been said: Ensure that the impulse response of your lowpass filter is shifted to the front of your time domain ...
alireza's user avatar
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Trade offs in window based design of FIR filter

Please find attached snap of proakis dsp book. It shows rectangular window has minimum value of stop band attenunation and transition width and as we go on towards Hamming and Blackman window,stop ...
DSP_CS's user avatar
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4 votes
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How does the effect of windowing change with the phase of the input signal?

I am calculating the SNR (signal power to noise power) for a sine wave. I don't have an integer number of periods in the waveform being analyzed, so I am using a flattop window to reduce spectral ...
DavidG25's user avatar
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Applying Hanning window $w_n=1-\cos\Big(\frac{2\pi n}{N}\Big)$ to data

I have a time-series data file in python and I am asked to apply a Hanning window $w_n=1-\cos\Big(\frac{2\pi n}{N}\Big), 0\leq n\leq N=\text{file length}$ to the data given. I am very new to this ...
LianNuo 's user avatar
2 votes
2 answers
172 views

FFT of 2 sine tones using windowing and zero padding. Wrong FFT amplitude

Here is my attempt to perform an FFT on a random signal with 2 tones in which I applied zero padding AFTER windowing. (I did not apply zero padding before windowing because that would suggest that the ...
shoggananna's user avatar
2 votes
1 answer
117 views

Correct Windowing Effect at Amplitude Scale

I am trying verify the noise floor returned by Matlab sinad(). I am able to get the results matching by summing power spectrum density with $\frac{f_\text{s}}{N}$. ...
John L's user avatar
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Determining minimum window length for DTFT [duplicate]

Let $x(t) = \cos(2\pi\times15t)+\cos(2\pi\times22t)+\cos(2\pi\times35t)+\cos(2\pi\times42t)$ and $\forall t\in\mathbb{R} :w(t) = 1$. We sample $x(t)$ and $w(t)$ with $F_s = 92 \ \text{Hz}$. So we ...
S.H.W's user avatar
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What is the right scaling factor to get the amplitude after aplying a hanning window? [duplicate]

I have a waveform where I sliced the flat top so I can do some analysis on the amplitudes of each frequency. I have a dataset of N measurements each with M samples of current (A) over time (...
Typhaon's user avatar
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4 votes
1 answer
167 views

Are there windows that create asymmetric sidelobes

I am working on a project which uses radar imaging. The radar imaging takes place at a relatively small distance from the radar (0.25m to 3m). The data is collected using an FMCW radar. The FFT of the ...
CMH12's user avatar
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2 answers
536 views

Converting a triangle from the frequency domain to the time domain

I’ve been given a triangular signal that looks like this: $$ X^{F}(\omega) = (2 -|\omega|) \cdot W_{[-2,2]}(\omega)$$ (this is just my interpretation of the signal from a picture I’ll add). I was ...
Piratemetaldrinkingcrew's user avatar
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1 answer
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Is Hann-windowing applicable when calculating a DTFT?

I have read that people often use a zero-padded DFT with Hann-windowing to get the amplitude+phase information at one frequency (where the Hann window is used to reduce the effect of a small/finite ...
Chillpadde's user avatar
1 vote
1 answer
1k views

What is the energy`correction or amplitude correction for a Tukey window?

From this page: https://community.sw.siemens.com/s/article/window-correction-factors there is a list of correction factors for popular windows. Is there a correction factor for Tukey window, depending ...
birki's user avatar
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2 answers
214 views

How does applying a unity-gain Hann window to White Noise change its power?

What works: I generate real-valued white gaussian noise with standard deviation $\sigma$ I calculate the FFT of this noise. The Abs of the FFT is a flat noisy trace over frequency, as expected for ...
tobalt's user avatar
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0 votes
1 answer
443 views

Window gain factor and amplitudes in FFT

I have some vibration data (acceleration) on which I need to perform an FFT, integrate it and again do an FFT. I read that for the nature of the data that I have, the input to the FFT must be first ...
Teja Jupudi's user avatar
2 votes
1 answer
326 views

Applying Kaiser Window to sinc interpolation

I am trying to apply the kaiser window during sinc interpolation. The following is my sinc interpolation code: ...
Hari's user avatar
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1 vote
1 answer
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Overlap correlation indices in Harris 1978

In the heavily cited paper by Harris 1978, there is a section on "Overlap Correlation" where he's using a "fractional overlap r" in his equation. Here is a screen shot from the ...
ThatsRightJack's user avatar
2 votes
1 answer
104 views

Window Choice of FFT

I am working with data from a TeraFlash THz Spectrometer from Toptica, which gives me the pulse in the time domain and the spectrum in the frequency domain I have been experimenting with the FFT to ...
lazerlini's user avatar
0 votes
3 answers
898 views

Number of periods of signal required when doing an FFT

I'm using numpy.fft in python to compute Fast Fourier Transforms. In particular, I'm using rfft as I have a real signal and don'...
Bern's user avatar
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1 vote
2 answers
523 views

How to generate a raised-cosine window with a specific roll-off factor in Matlab?

I have recently started working on signal processing. For a small project, I have to shape cosine signals using a raised-cosine window with certain roll-off factors in Matlab. To give you an example, ...
F105's user avatar
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0 votes
2 answers
220 views

Impact of STFT window function and FFT length on computation time

I have been doing a study which part of it includes a comparison of computation time vs window type and length (among some other things in the computation time, however I speak in terms of relative ...
rshah's user avatar
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0 votes
1 answer
175 views

Sampling, filters, windowing, FFT. From theory to help on this coding list

My plan is to analyse the spectrum of samples from a microphone. I wonder how correct this suggestion is. The below description may then fail on several points. I am in need of somebody with a red ...
Øyvind Teig's user avatar
3 votes
2 answers
664 views

Applying a window to a signal

How can I Gaussian or Bartlett window to a signal? On the other hand, is it a good way of smoothing signals? If not what are the differences between smoothing and windowing?
Kanan Suleyman's user avatar
4 votes
4 answers
560 views

FFT with High Time and Frequency Resolution

Can anyone describe in a bit more detail or provide references to the techniques for simultaneous enhancements to time and frequency resolution described in a high level in HEAD acoustics ...
Steve's user avatar
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2 votes
1 answer
473 views

Low-pass vs. windowing function in front of FFT

I am sampling sound at 48 kHz because that's what the DAC for the headset needs. I take every 6th of these. So I have 8 kHz and process 1024 at a time. My goal is to analyse the spectrum in the final ...
Øyvind Teig's user avatar
5 votes
1 answer
319 views

Complex Windows

Typically windows are symmetrical and real. Are there any applications where complex windows have been used (other than applying the same real window to the real and imaginary components of a complex ...
Dan Boschen's user avatar
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1 answer
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Understanding spectral leakage in a pink noise dominated signal

I've been reading about power spectral density estimation based on the DFT, about spectral leakage, windowing functions and the Welch method. I've recorded a signal that's supposed to be pretty much ...
Xaser's user avatar
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