white noise spectrum

I have use a simple LFSR to generare random number. Set of random number are pass through to FFT(power in db vs freq). However, the freq response is increasing at low freq. Then only maintain roughly flat for higher freq. Is there any problem with increasing at low freq?

If yes may i know the reason?

FYI, lot of white noise freq response is almost flat from low to high freq.
Link of the white noise spectrum:
http://www.2shared.com/file/10457498/8be6ec93/white_noise_spectrum.html

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Hi,

How are you measuring that spectrum, which insrtument -if any- are you using for that purpose? It looks like some DC blocking filer is present in the signal chain; if you are measuring by generating the randon mumbers on a PC and getting spectrum through sound card by using some PC utility, the HighPass filter efefct that you see there comes from the analog front end on your sound card itself.

Just my 2 cents.
 
Jaime Andrés Aranguren Cardona
j...@ieee.org
j...@computer.org

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Gesendet: Montag, den 4. Januar 2010, 22:07:41 Uhr
Betreff: [audiodsp] white noise spectrum

 
I have use a simple LFSR to generare random number. Set of random number are pass through to FFT(power in db vs freq). However, the freq response is increasing at low freq. Then only maintain roughly flat for higher freq. Is there any problem with increasing at low freq?

If yes may i know the reason?

FYI, lot of white noise freq response is almost flat from low to high freq.

Link of the white noise spectrum:
http://www.2shared. com/file/ 10457498/ 8be6ec93/ white_noise_ spectrum. html

Thanks

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Jason-

> I have use a simple LFSR to generare random number. Set of
> random number are pass through to FFT(power in db vs freq).
> However, the freq response is increasing at low freq. Then
> only maintain roughly flat for higher freq. Is there any
> problem with increasing at low freq?

The graph appears to show about 40% or so of the spectrum not flat (i.e. your "low freq" area).

The x-axis in the pic seems to be in samples, not frequency, so my guess is your FFT size was 1024. Is the random
number sequence also 1024 or did you zero-fill some of that? What if you double the sequence length... any
improvement?

-Jeff

> If yes may i know the reason?
>
> FYI, lot of white noise freq response is almost flat from
> low to high freq.
> Link of the white noise spectrum:
> http://www.2shared.com/file/10457498/8be6ec93/white_noise_spectrum.html
>
> Thanks Start a New Thread