Window functions

Started by in comp.dsp20 years ago 53 replies

Hi all. I'm playing a bit with window functions in filter design etc, and have come across a couple of gruelling expressions. More...

Hi all. I'm playing a bit with window functions in filter design etc, and have come across a couple of gruelling expressions. More specifically, the Chebychev window [1, eq. 5-17], the Tukey window [2, table 8.1] and the Lanczos window, [2, table 8.1]. I would like to know how one estimates the width of the main lobe for these filters, and how one uses the various control parameters....

Time derivative of Blackman window

Started by in comp.dsp15 years ago 13 replies

Hi, I've made a Blcakman window in Matlab with the...

Hi, I've made a Blcakman window in Matlab with the code: windowWidth=256; Window=(0:windowWidth)/windowWidth; Window=0.42-0.5*cos(2*pi*adaWindow)+0.08*cos(4*pi*adaWindow); This looks fine when I plot it, But Im not sure wether how to calculate the time derivative of it. An fft of the Window variable gives just a single peak and a flat line, and gradient(Window)*Fs doesn't look r...

how to do FFT on a series of data

Started by in comp.dsp14 years ago 4 replies

Hi all, My understanding is that FFT needs to operate on a window. If I want to look at the spectrum of a series data, I guess I have to...

Hi all, My understanding is that FFT needs to operate on a window. If I want to look at the spectrum of a series data, I guess I have to do a rolling-window, let's say N=256, The first window is from 1 to 256, and the second window is from 2 to 257, the third window is from 3 to 258, etc. For each window, I will have 256 numbers as the FFT outputs, What's the best way to present...

Why use such a window?

Started by in comp.dsp15 years ago 4 replies

I am studying a matlab function specsub.m,which perfom Martin's spectral subtrction method. specsub.m can be found in the lately voicebox. A...

I am studying a matlab function specsub.m,which perfom Martin's spectral subtrction method. specsub.m can be found in the lately voicebox. A new window usage attractted me and made me puzzle. what is charecteristic of the follwing window? Why use such a window? w=sqrt(hamming(nf+1))'; w(end)=[]; % for now always use sqrt hamming window w=w/sqrt(sum(w(1:ni:nf).^2)); % normal...

Triangle Window ?

Started by in comp.dsp13 years ago 15 replies

Is the triangle window pretty much lame or are there examples where the triangle window is the best window to apply to data prior to...

Is the triangle window pretty much lame or are there examples where the triangle window is the best window to apply to data prior to an FFT? Could anyone provide examples of when triangle window is the best choice?

Question about Gaussian window and parabolic interpolation

Started by in comp.dsp7 years ago 39 replies

I have done some experiments with a Gaussian window applied to real signals. The signals were pure sinusoids of a fixed frequency...

I have done some experiments with a Gaussian window applied to real signals. The signals were pure sinusoids of a fixed frequency and phase. I used this window: w(k) = e^( -(1/2) * (k - (N-1)/2)^2 / (a*(N-1)/2)^2 ) with N=32, k = 0, ..., N-1 and a = 0.265391249974779 I multiplied my signal with the window and did the DFT. Then I calculated the magnitudes around the peak. I took the...

Re: Appendix A: Types of Fourier Transforms

Started by in comp.dsp13 years ago 6 replies

On Friday, January 21, 2011 6:59:36 PM UTC-5, dbd wrote: ... > The window is how the user trades off locality and variance. It is an > ...

On Friday, January 21, 2011 6:59:36 PM UTC-5, dbd wrote: ... > The window is how the user trades off locality and variance. It is an > important tool in controlling the selected processing. It is useful to > put the window conceptually in the DFT because basis function values > outside the window are never calculated while the data values outside > the extent of the window are used.

Kaiser window vs Kaiser-Bessel window

Started by in comp.dsp14 years ago 7 replies

Hi, I am trying to use Kaiser-Bessel window before FFT. However, I am a bit confused about what is the difference between Kaiser and...

Hi, I am trying to use Kaiser-Bessel window before FFT. However, I am a bit confused about what is the difference between Kaiser and Kaiser-Bessel window. There is a definition of Kaiser window: http://en.wikipedia.org/wiki/Kaiser_window and also definition of Kaiser-Bessel derived (KBD) window. According to this document, Kaiser and Kaiser-Bessel windows are the same: http://local.wa...

FFT windows

Started by in comp.dsp18 years ago 3 replies

Does anybody know if the FTT window cos2n(t) have an official name. I call it the Moriat window because one of my frinds started a discussion...

Does anybody know if the FTT window cos2n(t) have an official name. I call it the Moriat window because one of my frinds started a discussion abot this window. Jens Hee www.jenshee.dk

Do I need a window?

Started by in comp.dsp14 years ago 16 replies

Hi I need to find out the frequencies present in the variation of a physical quantity from a discretely sampled data of finite length. Which...

Hi I need to find out the frequencies present in the variation of a physical quantity from a discretely sampled data of finite length. Which window (if any) should I use? I think doing an fftn in MATLAB uses a rectangular function by default. Please correct me if I am wrong. Also, is there a way to create a 2D version of a given window? Thanks and Regards

Why non'symmetric window in LP based speech coders (for instance CS-ACELP G729...)

Started by in comp.dsp21 years ago 3 replies

Hello, I'm studying LP based coders but couldn't find proper explanation why non symmetrical window (half Hamming and quarter of cosine) is...

Hello, I'm studying LP based coders but couldn't find proper explanation why non symmetrical window (half Hamming and quarter of cosine) is used. Is it because of magnitude response or time domain shape ? What is scientific background to use of this window ? How could I evaluate performance of some other window sequences - any tutorials (preferably Matlab) available to do such evaluation...

Four item cosine window constant derivation

Started by in comp.dsp17 years ago 2 replies

Hi, I'm looking for the method to get the Rife vincent window or other windows constant value. Take for example Blackman window which has...

Hi, I'm looking for the method to get the Rife vincent window or other windows constant value. Take for example Blackman window which has below equation: w(n)=0.42-0.5cos(2*pi*n/N)+0.08cos(4*pi*n/N), 0

Window size for digital filtering.

Started by in comp.dsp16 years ago 3 replies

This is a random question on a simple topic. Sorry if this is a little trivial. If you were to filter a signal with a windowed sinc...

This is a random question on a simple topic. Sorry if this is a little trivial. If you were to filter a signal with a windowed sinc filter, (using a Blackman window), would you get better results using a large 20,000 point window or a smaller 2,000 window? Consider the signal has no step functions or spikes, and it is a 250 sample per second signal. Consider the performance in the time domain ...

Reflecting negative frequency to positive frequency

Started by in comp.dsp9 years ago 6 replies

I am trying to sample the magnitudes of a shifted window in the frequency domain. But I wonder what to do when a part of the window sits in the...

I am trying to sample the magnitudes of a shifted window in the frequency domain. But I wonder what to do when a part of the window sits in the negative frequency. Here is an example: if the window (ps. a real symmetrical, ie. H[-k] = H[k]) is centered at 80 Hz, and the sampling interval (the interval between two bins) is 43 Hz. These are the bins around the center of the window to be sampled:...

Optimum Window Duration

Started by in comp.dsp18 years ago

Hi all we are doing a voice verification project in MATLAB. I have done a pitch detection algorithm which is working ok ok depending on...

Hi all we are doing a voice verification project in MATLAB. I have done a pitch detection algorithm which is working ok ok depending on the length of the input as well the length of hamming window. Now for male input, the results are quite good if the window duration is 120-150 samples (sampling rate is 8 KHz) whereas for female voice i have to reduce window length to almost half if the voi...

Sliding window FFT

Started by in comp.dsp19 years ago 2 replies

Hi, I am trying to understand the difference between the sliding window FFT algorithm and the windowed FFT (i.e. the conventional...

Hi, I am trying to understand the difference between the sliding window FFT algorithm and the windowed FFT (i.e. the conventional method). Say we have a 6000 sample time domain data that we wish analyze in frequency. We can take two approaches: 1- Pad the data stream with 2192 zeros and apply a 8192 point FFT. 2- Choose a short window size (e.g 256 points) and slide this window acros...

Fast True RMS averaging how? My current method is slow.

Started by in comp.dsp16 years ago 5 replies

Hi all, I'm playing around with an audio level compressor and calculate the RMS value in a rectangular window. I'm quite new to this ( also to...

Hi all, I'm playing around with an audio level compressor and calculate the RMS value in a rectangular window. I'm quite new to this ( also to dsp programming ), but my questions are: - Is there an optimum size for the averaging window? The bigger the window the more true the average RMS will be, i think. But a big averaging window takes too much load on the processing power of my dsp. ...

Window function

Started by in comp.dsp20 years ago 10 replies

Hi, I am looking for a window function that doesn't smear frequencies that fall exactly into a frequency bin. I thougt the Hann window is a...

Hi, I am looking for a window function that doesn't smear frequencies that fall exactly into a frequency bin. I thougt the Hann window is a good choice, but it still produces some smearing. Is there a better choice? Regards, Christian

"zero phase" FFT windows

Started by in comp.dsp19 years ago 4 replies

Hi All, Has anyone else played around with "zero phase" windows for STFT? The idea here is that instead of the "conventional" way of applying...

Hi All, Has anyone else played around with "zero phase" windows for STFT? The idea here is that instead of the "conventional" way of applying the window where the zero'th window coefficient is applied to the zero'th input sample in the FFT buffer etc. and all of the zero padding (if any) is applied at the end, with a zero phase window you apply the centre coefficient of the window to the z...

sliding window and compare signals in simulink

Started by in comp.dsp18 years ago 1 reply

Hello. I have a problem in Simulink. What i want to do is take one signal from workspace (which initially was a .wav file), and aply a sliding...

Hello. I have a problem in Simulink. What i want to do is take one signal from workspace (which initially was a .wav file), and aply a sliding window on it. The signal is frame based, single channel. Next i want to compare each window that slides thru the signal with a second signal, which size is exactly the sliding window size. In other words, let's say we have the word "abracadabra" repres...