## Forums Search for: Windowing

## Windowing spec. analyzer?

inI know there are spectrum analysis programs that have a zoom function, ie. you can limit the graphical display to show only a small...

I know there are spectrum analysis programs that have a zoom function, ie. you can limit the graphical display to show only a small frequency range within the sampled bandwidth. What I am looking for, however, is a program that will only FFT that small frequency range (user specified), instead of the entire sampled bandwidth, so resolution within it can be maximized. Has anyone seen anyt...

## Windowing

inHello, I'm new to dsp, still much to learn. I'm working on something that will apply window function to signal read from a .wav file. Until...

Hello, I'm new to dsp, still much to learn. I'm working on something that will apply window function to signal read from a .wav file. Until now I've developed a code that reads the data and loads it into memory buffer. The code looks like: "int main(int argc, char *argv[]) { FILE *fwyj,*fout; double ts,tk,time; float f0,pr,window; int z,N; long start_byte,end_byte; long new_d...

## "Smoothing" a Frequency Response

inHello, Is it possible to intelligently smooth an experimentally gathered frequency response? I have input and output time history signals,...

Hello, Is it possible to intelligently smooth an experimentally gathered frequency response? I have input and output time history signals, to which I apply an in-house FFT/windowing/smoothing program to compute the gain, phase, and coherence. I then compare the results to an analytically generated response. On many of these runs, the higher end of the measured frequency response is very "n...

## autocorrelation for frequency estimation question

inWhen using an fft for frequency estimation of a complex audio waveform (singing voice, piano, etc.), the bin representing half the...

When using an fft for frequency estimation of a complex audio waveform (singing voice, piano, etc.), the bin representing half the fundamental frequency will be mostly empty. Won't the bin of the autocorrelation result for double the wavelength of the fundamental frequency have some energy in it? How does one handle this false positive? Also, the fft of short segments requires windowing f...

## Phase is affected by windowing?

inHello for everybody!!!!!!!!!!!!! I write a program for FHT(Hartley) and i wtite a flat top, hanning and hamming window function everything is...

Hello for everybody!!!!!!!!!!!!! I write a program for FHT(Hartley) and i wtite a flat top, hanning and hamming window function everything is ok here. Im analysing 2 signal of 60 Hz both. v=sin(2pif) i=sin(2pif-theta_i) theta=theta_v-theta_i if theta_i is between 0-27 degrees and theta_v=0 there?s no problem theta= angle between 0-27 but if theta_i is for example 28 or more (theta_v = ...

## Spectrogram Plot to Bitmap Output

inHi Everyone, I'm looking to make a small C/C++ command-line utility which takes a binary audio file as input and generates a spectrogram of a...

Hi Everyone, I'm looking to make a small C/C++ command-line utility which takes a binary audio file as input and generates a spectrogram of a given time range of the file. First off, I am already comfortable with reading/writing binary audio files, as well as the "back end" requirements for generating spectrogram information (FFT, windowing, etc.). What I am not familiar with is gener...

## Averaging incoherent (noncoherent?) samples

inI'm testing an A/D converter and need to average several acquired data sets to improve SNR. I've done this in the past with coherently sampled...

I'm testing an A/D converter and need to average several acquired data sets to improve SNR. I've done this in the past with coherently sampled data, but in this case the data is not coherent and I'm not sure how to proceed. I've tried windowing the data sets individually then averaging, but that didn't work. I don't have sufficient control over the instrumentation to force coherent sampling. Th...

## DSP Spectral Analysis using MATLAB

inHi everyone, I am new with matlab and am having problems with a spectral analysis problem i'm trying to do. I need to perform spectral analysis...

Hi everyone, I am new with matlab and am having problems with a spectral analysis problem i'm trying to do. I need to perform spectral analysis of a signal consisting of 1000Hz, 1000.1Hz and 999.9Hz i.e., x=cos(2*pi*1000*t)+cos(2*pi*1000.1*t)+cos(2*pi*999.9*t) so that all the three peaks are seen. This is to be done using a windowing function like blackmann-harris/guassian. I wrote the m-...

## Spectral Analysis using MATLAB

inHi everyone, I am new with matlab and am having problems with a spectral analysis problem i'm trying to do. I need to perform spectral analysis...

Hi everyone, I am new with matlab and am having problems with a spectral analysis problem i'm trying to do. I need to perform spectral analysis of a signal consisting of 1000Hz, 1000.1Hz and 999.9Hz i.e., x=cos(2*pi*1000*t)+cos(2*pi*1000.1*t)+cos(2*pi*999.9*t) so that all the three peaks are seen. This is to be done using a windowing function like blackmann-harris/guassian. I wrote the m-...

## Name of this window

inI've started using a simple windowing function to low pass filter a 2D image. Following the FFT, I multiply in the frequency domain with...

I've started using a simple windowing function to low pass filter a 2D image. Following the FFT, I multiply in the frequency domain with a function that increases with distance from the origin (allowing for wrapping). Then I IFFT back to the image domain. Basically the window is this: f = sqrt(alpha / (alpha + x^2 + y^2)) where x,y range from 1-n/2 to n/2 and alpha is a scalar. Anyone k...

## Usage of windowing for FFT order analysis

inHi; I have an algorithm in VBA that: -takes the sampled (500-1000 Hz) Torque signal, and splits it up into sections that correspond to each...

Hi; I have an algorithm in VBA that: -takes the sampled (500-1000 Hz) Torque signal, and splits it up into sections that correspond to each revolution of the machine. - For each revolution of torque data, I interpolate the data to fit a power of 2 samples for the FFT algorithm. - I take the FFT of each revolution of torque data, and then chop all but the 1st 4 orders of the spectrum. ...

## Why (if) should be windows in spectral analysis nonnegative ?

inHello, I'm reading a lot of literature on windowing in spectral analysis but haven't found theoretical cause of background for statement that...

Hello, I'm reading a lot of literature on windowing in spectral analysis but haven't found theoretical cause of background for statement that windows sequences should be nonnegative. It seems logical that weighting should be done with positive factors but since gained frequency response is convolution integral between "real" response and window's response there seems to be no cause for no...

## Nyquist, quantization and windowing gotcha's

inI've been experimenting with a 3D version of spectrograms [amplitude vs frequency vs time]. Instead of plotting the spectrum of each time slice...

I've been experimenting with a 3D version of spectrograms [amplitude vs frequency vs time]. Instead of plotting the spectrum of each time slice (cf waterfall displays), I plot contours of equal amplitude across time. Borrowing from traditional spectrograms, each contour's color also indicates amplitude allowing adjacent contours to be distinguished when close together. The observed ar...

## six DFT window functions applied to a 64 point DFT

inHi, I have created a new flash program that shows how windowing is used to reduce leakage in a DFT. The program also discussed magnitude...

Hi, I have created a new flash program that shows how windowing is used to reduce leakage in a DFT. The program also discussed magnitude and power representation of the DFT coefficients. The program allows you to run a 64 point DFT. The DFT allows two frequency inputs with variable gain on the input levels of each frequency. You can apply six window functions and vary the signal...

## Wiener adaptive filtering and windowing: discontinui

inHi all, I wrote a simple adaptive wiener filter in matlab to remove noise from an audio file. The routine computes correlation matrixes on a...

Hi all, I wrote a simple adaptive wiener filter in matlab to remove noise from an audio file. The routine computes correlation matrixes on a rectangular window of 256 samples but I have difficulties when rebuilding the whole file: on every edge of the filtered windows I have a discontinuities, so the global result is corrupted. http://img208.imageshack.us/img208/950/wiener4kq.jpg Cou...

## Spectral analysis

inHi, I am familiar with computing the spectrum of a real time signal using FFT after windowing it using a window such as hamming to increase...

Hi, I am familiar with computing the spectrum of a real time signal using FFT after windowing it using a window such as hamming to increase the resolution of the spectrum, however I need to compute the spectrum of a complex signal, can anybody explain how to window a complex signal before computing the FFT. Thanks Tom

## Overlap-Add Question

inHi, I have a question about the overlap-add technique. I am taking some raw audio data and I'm windowing it with 4096 point FFTs (and throwing...

Hi, I have a question about the overlap-add technique. I am taking some raw audio data and I'm windowing it with 4096 point FFTs (and throwing away the data that is reflected so I get 2047 points for each window). The windows are non-overlapping. In the frequency domain, I set some frequency bins to zero and then I do an IFFT with each window (making sure to put back the reflected data) wh...

## Denoising and envelop detection

inHi, I am working on radar processing and I am new to this study. I have 1D time domain data and I used windowing technique and 'fft'ed the data...

Hi, I am working on radar processing and I am new to this study. I have 1D time domain data and I used windowing technique and 'fft'ed the data and plotted the data using imagesc and it is a spectrogram. My question is to denoise the spectrogram and to extract the data from the envelope obtained in the spectrogram. I am working this study in Matlab. Can any one suggest me denoising algorithm and e...

## windowing question

inSuppose that I have a continous-time signal that consists of a finite number of Dirac impulses at integer time points. For example, lets say the...

Suppose that I have a continous-time signal that consists of a finite number of Dirac impulses at integer time points. For example, lets say the signal starts at t=0 and lasts for 100 seconds, with 100 dirac impulses, one per second. It's easy to take the Fourier Transform of this signal, since it is time-limited. Now lets apply a rectangular window to this signal, such that only 50 sec...

## MFCC

inHi all, long time reader, first time posting as a member. My query relates to MFCC calculation. Generally speaking I have an ok verbal...

Hi all, long time reader, first time posting as a member. My query relates to MFCC calculation. Generally speaking I have an ok verbal understanding of MFCC's, however I never had a detailed understanding. Firstly, im trying to implement this in MATLAB (this being MFCC calculation). Im fairly all right at MATLAB, so the previous steps to MFCC calculation such as windowing and framing a...