Windowing and spectrum amplitude

Started by Alberto in comp.dsp15 years ago 16 replies

I have a program that does real time spectral analysis of audio signals. If I interactively change the window used before the FFT,...

I have a program that does real time spectral analysis of audio signals. If I interactively change the window used before the FFT, choosing between Hamming, Hann, Balckman, etc. etc I can of course see the widening or the narrowing of the peaks corresponding to steady frequencies, but I notice also a changing value for the amplitude of the peaks, depending on the window used. I compute the v...


FFT and windowing for a newbie

Started by goatman in comp.dsp15 years ago 7 replies

Hi there, Just a quick question from a DSP beginner here. I'm doing a college project on basic speech recognition, and I have some questions. I...

Hi there, Just a quick question from a DSP beginner here. I'm doing a college project on basic speech recognition, and I have some questions. I am told to use a 256 point FFT with a hanning window and 50% overlapping. This then produces a number of FFT windows right? (for example, in a 512 sample sound file I will have 3 windows). Then I have to perform an FFT on them. I then need to apply a...


Help required to use MFCC for speaker recognition

Started by AMIT kaul in comp.dsp15 years ago 5 replies

I want to use MFCC for the task of Speaker recognition but inspite of following the Steps given below i have not been able to...

I want to use MFCC for the task of Speaker recognition but inspite of following the Steps given below i have not been able to discriminate between the speakers 1)windowing 2)fft 3)power spectrum(p) 4)using melscaled filter bank f'*p(whether this is mel warping or it is something else) 5)log 6)DCT(mfccs) if there is any paper which explains which explains what exactly is melfrequency w...


Time Scaling using Phase Vocoder

Started by Rob Vermeulen in comp.dsp15 years ago 5 replies

Hello, I am pretty new to the topic of DSP. However, I do have some practical experience with FFT and windowing. Now what I like to have is...

Hello, I am pretty new to the topic of DSP. However, I do have some practical experience with FFT and windowing. Now what I like to have is some explanation of how to implement a phase vocoder to create a (real-time) time compress/expand algoritm. Ofcourse I've been wandering around google for quite some time and I did see some already-made implementations for the Windows platform. But th...


Increasing Notch depth using windowing

Started by ravash in comp.dsp11 years ago 3 replies

Hello everyone, Hope no introduction for why I am here (I have a problem.....) Presently i am working on a ofdm simulink implementation...

Hello everyone, Hope no introduction for why I am here (I have a problem.....) Presently i am working on a ofdm simulink implementation where I need to increase the single carrier notch depth (notch is created by putting some carriers to zero)which at present is 13dB(because of 'no window' or default 'rectangular' window implemented). I am using a raised cosine window for the same so as to ...


Peak Windowing for OFDM

Started by Crisanquito in comp.dsp10 years ago 8 replies

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am...

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am using is a Gaussian window, with factor gamma (exp(-gamma*t^2)) I have already implemented it, but I do not know if the results obtained are so satisfactory as they should be. My concern is on the proper choice of the value gamma: I make it inversely prop...


FFT: Zero-padding, Windowing - What order?

Started by Marc Jenkins in comp.dsp6 years ago 19 replies

Hi, I have a question regarding FFT: If I want to calculate the FFT of a signal I would extend the signal to the next power-of-2 length to...

Hi, I have a question regarding FFT: If I want to calculate the FFT of a signal I would extend the signal to the next power-of-2 length to exploit the properties of the FFT. This is done using a simple zero-padding. If I window my signal to reduce leakage, when should this be done? Before or after the zero-padding? Thanks! Kind regards Marc


FIR windowing design

Started by pinkisntwell in comp.dsp10 years ago 35 replies

Let's say I decide on a desired frequency response, for example a highpass filter with zero phase. I can then take the samples of that frequency...

Let's say I decide on a desired frequency response, for example a highpass filter with zero phase. I can then take the samples of that frequency response and take their inverse DFT to get the impulse response of a truncated IIR system, essentially windowed with the rectangular window. I can then calculate its frequency response and plot it: http://i47.tinypic.com/vrg941.png If I apply the ...


Disperately seeking Hilbert filter coefficients

Started by Giuseppe Sbarra in comp.dsp14 years ago 11 replies

Hi everybody thanks to the support I received on a previous post I have been able to get working my implementation of a 90 degrees phase...

Hi everybody thanks to the support I received on a previous post I have been able to get working my implementation of a 90 degrees phase shifter, all I need now is a good guy which can calculate and post for me the coefficients for a 67 order Hilbert with Hamming windowing, because my tool just reach 35, or some reference to a free tool on the net for this job. ( I'm not planning to buy a 1K...


Windowing spec. analyzer?

Started by Charles davis in comp.dsp15 years ago 4 replies

I 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...


coherent sampling and I/Q demod

Started by petethepop in comp.dsp14 years ago 1 reply

(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In...

(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In this case the 'sine wave' I'm locked to is being sampled at x4 the sine frequency. This would seem to satisfy the coherent sampling requirement that regarding the digitizer clock. next question - coherent sampling removes the need for windowing in FFT ap...


FIR LPF Filter Designing by windowing

Started by ashwinss in comp.dsp11 years ago 1 reply

Hi, I am using FIR digital filters,but since i am new to this concept,i have stuck at one doubt.Please help me out. i am designing a LPF having...

Hi, I am using FIR digital filters,but since i am new to this concept,i have stuck at one doubt.Please help me out. i am designing a LPF having 6Hz & 30Hz passband & stopband edge freq Also Fs(Sampling) is 512Hz with hamming window. I have got the filters coefficient (which are a real one)by implementing it in matlab but on the site from where i am taking guidance of this topic they have got coef...


PSD-Frequency Bin?

Started by Kevin W in comp.dsp11 years ago 9 replies

I have a question about the PSD estimation and where exactly does the 'Hz' term come from on the unit denominator. After taking the 1024pt...

I have a question about the PSD estimation and where exactly does the 'Hz' term come from on the unit denominator. After taking the 1024pt FFT of a signal (let's say discrete vibration data sampled at 5kHz), we will get a plot of G vs Frequency (Hz)) with frequency resolution of 4.88Hz per data point. From my understanding of the PSD estimation (without windowing), we will square the ma...


SNR estimation using a windowed FFT

Started by Anonymous in comp.dsp12 years ago 4 replies

Hi, What is the best way to estimate the SNR of a sinusoidal signal in white noise using an FFT? For the best SNR estimate, is it better...

Hi, What is the best way to estimate the SNR of a sinusoidal signal in white noise using an FFT? For the best SNR estimate, is it better to do one long FFT or to break up into smaller FFTs to average the noise power? Also does windowing have an effect on the measured SNR? Thanks, Rizwan


windowing DFT vs FFT (newbie)

Started by Thomas Magma in comp.dsp16 years ago 1 reply

Hello, I wrote a program in Java that does a DFT on raw 8bit samples stored in memory from a RF ADC (Post processing). This allows me to...

Hello, I wrote a program in Java that does a DFT on raw 8bit samples stored in memory from a RF ADC (Post processing). This allows me to easily adjust the span (zoom) when I'm viewing the spectrum. Works great, but slow as hell. So I'm now trying an FFT with a Chirp Z-Transform so I can zoom in on the desired frequency and look for subtle modulation characteristics. I borrowed this code fr...


"Smoothing" a Frequency Response

Started by Roy in comp.dsp11 years ago 7 replies

Hello, 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...


Signals on FFT bins, and Windowing

Started by analog_fever in comp.dsp9 years ago 1 reply

I have an input signal that is generated using the following statements. Fs = 1.4287e6 (Sampling Frequency) Fbin = 32 (FFT Bin Number) N =...

I have an input signal that is generated using the following statements. Fs = 1.4287e6 (Sampling Frequency) Fbin = 32 (FFT Bin Number) N = 2^17 (FFT points) t = 0:N-1 input = A*Sin(2*pi*(Fbin/N)*t) I send this input through a Delta Sigma modulator. And then decimate it by 100 using a CIC decimation filter. Now the question is 1. I thought that the equation I use to generate the input,...


FFT, windowing & hop

Started by Rolf Keller in comp.dsp15 years ago 1 reply

Hi, I' m using an FFT with a Kaiser window and a hop of 50 %. 50 percent seemed to be theoretically optimal to me. But recently I read...

Hi, I' m using an FFT with a Kaiser window and a hop of 50 %. 50 percent seemed to be theoretically optimal to me. But recently I read that my idea is wrong and that the optimal hop depends on the shape of the window. The goal is that the contribution delivered by any individual sample to the final result does not depend on the random points of time where the window begins resp. en...


Nyquist, quantization and windowing gotcha's

Started by Richard Owlett in comp.dsp11 years ago 4 replies

I'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...


Averaging incoherent (noncoherent?) samples

Started by dcarr66 in comp.dsp13 years ago 12 replies

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...

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...