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

learn more… | top users | synonyms

0
votes
3answers
70 views

What exactly is the effect of a Hann Window on the FFT output?

In the code I am trying to understand, there is an usage of Hann window multiple times (There's overlapping frames, the size of each is 512 and the overlapping factor is 75% so each time we capture ...
0
votes
3answers
67 views

A question about spectral leakage

I have read about spectral leakages in other posts here. From what i understand, it occurs because you dont have an integer number of time periods in your sampled data. By default a rectangular window ...
1
vote
2answers
39 views

Spectral leakage - understanding the integer number of cycles while windowing

I am reading tutorials about windowing and have read following sentence: For an integer number of cycles, all smoothing windows yield the same peak amplitude reading and have excellent amplitude ...
0
votes
2answers
50 views

is there a mathematical relation between percent overlap and window length or amplitude

I am trying to plot short time energy of an utterance with percent overlap as an input variable. As I referred to the short time energy equation it can be represented as square summation of ...
0
votes
1answer
58 views

Is there a closed form expression for main-lobe width increase given a window?

We know that when we window a signal, we increase the main-lobe width. Let 'main-lobe-width' here be the null-to-null bandwidth of the main lobe. Let us further more say that the main-lobe width of a ...
0
votes
2answers
152 views

Convolution in the frequency domain

We often hear that "convolution in time is the same as multiplication in frequency", and vice versa, that "convolution in frequency is the same as multiplication in time". So in a typical windowing ...
1
vote
1answer
60 views

What is the difference between Filters and Windowing?

I'm finding some difficulties to understand the difference between Filters, and Windowing. accoriding to my understanding both filters and window functions will make changes to the input signal ...
0
votes
0answers
27 views

How to acquire the `mainlobe` width to be less than the separation between two components that we wish to distinguish?

How does the mainlobe width of your window affect your ability to resolve the two components? Suppose a safe choice is to ...
0
votes
4answers
163 views

FFT - Effects of Windowing,Improvisation approaches on RealTime FFT Hardware

Fore-word :Kindly Observe this question has multiple updates take the latest update as question ! here below is my 256pt FFT on an 2Khz sinusoid signal,on a fixed point DSP tms320c5515 please ...
0
votes
0answers
46 views

STFT - Stride the windows?

In matplotlib's spectrogram function, this is how they "seperate and overlap windows": result = stride_windows(x, NFFT, noverlap, axis=0) What this is doing: ...
1
vote
2answers
58 views

STFT - Putting it all together

I'm currently reading this paper: http://www.rssd.esa.int/SP/LISAPATHFINDER/docs/Data_Analysis/GH_FFT.pdf On page 21, it has a section called "Putting it all together", it states the following ...
1
vote
1answer
221 views

Effect of Hanning Window on phase of FFT

I'm calculating the beat of song through the frequency domain. I have 60 seconds of audio sampled at 48000Hz, multiplied by a Hanning window in the time domain. This gives me a resolution in the ...
0
votes
1answer
41 views

phenomenon when window size for STFT is too short

Hi I was researching on STFT when I encountered this slide online I don't understand the points, Can anyone explain them? Thanks in advance.
0
votes
1answer
74 views

gabor wavelet and gabor transform

I was reading a paper 'A Flexible Framework for Local Phase Coherence Computation' (paper URL) on using wavelets for local phase coherence. I just want to be sure. Is the gabor wavelet the same as the ...
0
votes
3answers
149 views

Zero-pad before or after windowing for FFT

What's the correct way. Should I zero-pad a signal before or after applying a windowing function?
2
votes
2answers
212 views

Working around FFT windowing?

I have the following problem, that I ran into recently, when calculating the spectra of data that I obtain from a measurement technique, we are using in our group. In short what we do in the ...
2
votes
3answers
301 views

Choosing the right overlap for a window function

On Wikipedia there is quite a list of window functions. However, when you are doing a lot of STFTs, you often have to have some overlap to get better results. Generally an overlap factor of 2 (i.e., ...
0
votes
5answers
133 views

To what extent can we see signals that fall between frequency bins?

I have a simple problem I would like to figure out for fourier analysis of seismic data. Let us say that we have a signal $z[n]$, of length $N$. If I take its (same size) FFT, I will get $Z[k]$, ...
1
vote
0answers
72 views

Short term energy signal explanation

I'm trying to calculate the short term energy of a digital signal in python, using a rectangular window, but don't understand the basics of how this works, a pointer to any good explanation would be ...
0
votes
1answer
65 views

frequency components of discrete Gaussian-windowed signal

When we are do a discrete Gabor transform on a 1D signal, we apply a Gaussian window on a segment of the signal. However, due to the tapering ends of the Gaussian window, the magnitude of the data ...
1
vote
1answer
56 views

How do you choose a size for a windowing function in FFT?

How does one choose the proper windowing function to apply in an FFT? What are the benefits of larger sizes and smaller ones? Which would be the best for pitch estimation? Also which window function ...
2
votes
1answer
375 views

Why should one use windowing functions for FFT?

So I just revised my pitch calculation algorithm using a harmonic product spectrum algorithm. I was just curious about why this explanation of Harmonic Product Spectrum states that you need to ...
0
votes
2answers
896 views

Split audio signal into frames, apply window function and merge again

First off: I'm really new in the signal processing department and MatLab as well, so please bear with me here. What I want to achieve is to split my audio signal into smaller 25ms frames, where the ...
0
votes
1answer
272 views

Relationship between frame rate and sampling frequency in speech signal processing?

While I was going through the short time processing of speech signals, I got stuck at the relationship between the frame rate and the sampling frequency. Is there any relationship between them for ...
0
votes
1answer
101 views

STFT zeropadding

I am trying to implement the STFT by MATLAB, and I read somewhere that we must do zeropadding to the subsequence of the signal before windowing it with a Gaussian window. What happens if we don't do ...
2
votes
0answers
473 views

Matlab: Estimating power spectral density of an experimental data?

How do I estimate PSD in matlab ? There are lots of methods to estimate, depending on application. I am using an experimental data to identify faults ( e.g. interturn fault of electric motor), which ...
1
vote
1answer
124 views

What is the physics behind the width of a main lobe?

We know that the square window gives the lowest main lobe width possible, and that other windows after that trade main lobe width for side lobe height. I also understand that the main lobe width is ...
0
votes
0answers
72 views

instantaneous frequency

If my signal is $$ f(t)=\exp[i\phi(t)], $$ how do I show that $$ \int_{-\infty}^{\infty} {\xi}\left|S_f(u,\xi)\right|^2 d\xi = 2\pi\int_{-\infty}^{\infty} {\phi'(t)}\left|g(t-u)\right|^2 dt, $$ ...
0
votes
0answers
64 views

What is the correct way to calculate multi-taper estimates of spectral coherence?

I am trying to calculate the spectral coherence for two time-series using the multi-taper method. I am currently using Kiss-FFT to perform the Fourier transform. For calculating multi-taper ...
6
votes
1answer
228 views

Is the discrete Gaussian kernel an eigenfunction of the DFT?

So the Gaussian function is an eigenfunction of the Fourier transform because it transforms into itself, right? But this isn't true for the sampled Gaussian in the DFT because the tails of the ...
1
vote
1answer
130 views

STFT - Window Functions

I'm looking for your opinions. I have obtained a Speech Signal and computed a STFT on this signal. I have split the signal into blocks of (100 x 256) and computed the STFT based on different ...
3
votes
1answer
191 views

Matching masked images

Let's say I have two images that are parts of the same bigger image, cut using two masks (for simplicity, let's assume that the masks are just rectangles of the same size). The images are presumed to ...
1
vote
1answer
448 views

Frequency response <-> Impulse response

I am trying to calculate an actual frequency response from a desired frequency response. fftSize = 128; fs = 8000; I have 2 input arrays: f[] and aDesired[], ...
0
votes
2answers
4k views

How to apply Hamming Window?

I am new in matlab and signal processing. The time series that have been used are obtained from accelerometer in a building. As far as I understand both the time series' length and window function ...
0
votes
2answers
189 views

Intuitively, why is windowing function a low-pass filter?

I'm trying to intuitively understand why a windowing function of a signal is a low-pass filter. I know its DTFT is a sinc function, making it mathematically a low-pass filter, but my logic says ...
5
votes
5answers
2k views

Why do we use window in time domain rather than do FFT modify the spectrum and than inverse FFT

I thought that DSP would be done by using FFT of portions of a signal, modify the samples that result from FFT (since they represent the spectrum of our signal + noise) and remove any unwanted signals ...
5
votes
3answers
1k views

Effect of windowing on FFT magnitude

I have 2 sin waves: Fs = 1500; N = 100; t = (0:N-1)'/Fs; sinwave = sin(2*pi*15*t); sinwaveshifted = sin(2*pi*15*t + 1.3); If I get the magnitude at 15Hz using ...
2
votes
1answer
183 views

how do windowing functions not distort the signal?

I'm trying to gain a better understanding of windowing functions, but so far I can't tell why they're used. As an example, I'm familiar with the Hamming Window: $ w(k) = 0.54-0.46cos( ...
2
votes
3answers
237 views

best window for close frequency components

I'm currently designing a receiver which has to determine whether a signal contains specific frequencies or not. The frequencies are at constant 215Hz difference: ...
0
votes
2answers
201 views

PSD of Windowed signal

Suppose PSD of a signal $x(n)$ is $ PSD_{xx}(w)=1$. Now if a window function w(n) of length $ 0\le n \le N-1$ is applied to $x(n)$. what will be the new PSD?
1
vote
2answers
154 views

Applying Window Function to Low Frequency Signals

I'm computing 1 sec. hanning windows from a signal that has a variable frequency between 1-4Hz. My first impression is that data loss caused by the distortion due to the window function is greater ...
2
votes
1answer
377 views

Effect of Windowing Function on Autocorrelation Function

I need to compute FFT components and autocorrelation of a discrete signal. When I do not use any window function before taking FFT of the signal I get a reasonable AC function from FFT that includes ...
3
votes
1answer
144 views

Channel Vocoder producing output with “click” sounds

I'm trying to make a channel vocoder that takes two inputs, one a frequency rich carrier (a musical sound) and the other a modulator (vocals). Applying operations involved in the channel vocoder ...
9
votes
3answers
425 views

A few questions about Slepian and generalized gaussian windows

I'm trying to add documentation for all the window functions in scipy.signal, and I'm stuck on the Slepian (same as DPSS?) and Generalized Gaussian windows, which I'd never heard of before. There are ...
10
votes
2answers
688 views

FFT with asymmetric windowing?

Common non-rectangular window functions all seem to be symmetric. Is there ever a case when one would want to use a non-symmetric window function before an FFT? (Say if the data on one side of the ...
6
votes
3answers
911 views

What is a good FFT window function to reject DC?

I'm using an FFT to analyze what is essentially the power envelope of a signal (see here for info on the containing project), and, since power numbers are always positive, to eliminate the DC ...
3
votes
3answers
307 views

I need advice about how to make an audio frequency analyzer

I just need some clarification of some very basic aspects of creating a frequency analyzer. I am writing a c++ program, so far it is just a media player, with a custom explorer. You can make ...
6
votes
2answers
3k views

How do I apply a function window to a signal?

How can I apply a window function like Hamming or Lanczos to a signal, using its coefficients? I mean, which method can I use to do this? FFT? Convolution? Which method has the better performance?
5
votes
1answer
335 views

Spectrum Analysis using Windowed FFTs

I have a couple of questions regarding windowed FFTs: 1) Why is the noise floor higher with windowed FFTs (according to Wikipedia's spectral leakage page, anyway), when the whole point of windowing ...
4
votes
2answers
389 views

Whats the optimal window function to use for analyzing real-time data samples?

Say you wanted to run a X point FFT on the last X audio samples that were played. The problem being, using a normal hann window function would place emphasis on the "middle" of the audio sample. ...