Computer white noise generator, which software?

Bricolo

Member
2002-11-11 6:52 am
I'm trying to make some bandwidth measurements, but the white noise generator software I'm using is far from optimal.

For the moment, it's spectralab build in signal generator, but the spectrum is far from a straight line :(

Does anyone have a good white noise generator? The attached picture is what I get from spectralab, directly recorded from the wave device (so 100% software, it's not line in shorted to line out) with a 2x averaging
 

Attachments

  • image1.jpg
    image1.jpg
    35.2 KB · Views: 186
MERSENNE TWISTER is just an algorythm.
if you have matlab look here
you can run the function, normalize values to +-1 16-bit and save a vector of values as a wave ( command: wavsave() )

regards

P.S. there doesn't exist 'true' digital white noise generator, all are based on pseudo-random numers generators
 
What kind of details to you want? A basic setup configuration for testing line-level gear?

Use either the left or right line output from your soundcard and "Y" it....one leg back to one of the line inputs and the other leg to your DUT. The output of your DUT goes to the other line input. Select "real transfer function" from the dual-channel processing box in the options menu and activate the white or pink noise generator. Increase the averaging setting so you get nice smooth curve results.

A similar setup will work for close-miked speaker measurements if you incorporate a microphone and preamp into setup.

Cheers,

Davey.
 
Bricolo said:
I'm trying to make some bandwidth measurements, but the white noise generator software I'm using is far from optimal.

For the moment, it's spectralab build in signal generator, but the spectrum is far from a straight line :(

Does anyone have a good white noise generator? The attached picture is what I get from spectralab, directly recorded from the wave device (so 100% software, it's not line in shorted to line out) with a 2x averaging


Another way to obtain quite accurate and flat spectra in bandwidth measurements is measuring the impulse response of the system (using MLS signal, that is similar to white noise) and taking its FFT.

This is an example of the FFT of a loopback impulse response of a normal soundcard:


[IMGDEAD]http://purebits.com/images/apnot30.JPG[/IMGDEAD]

[IMGDEAD]http://purebits.com/images/apnot26.JPG[/IMGDEAD]

taken from http://purebits.com/appnote6.html


Bye,
Paolo
 

da_madaxeman

Disabled Account
2003-07-18 6:53 pm
Adelaide
I havn't read the whole thread so I may be off topic, but yes CEP2 (Cool Edit Pro 2) has a white noise generator and allsorts of other goodies (inc. multitrack recording :D ) and last I checked (a few years ago...) cost $20. OR you could get it off of a file sharing network............. And, er, register it asap of course :p
 

Bricolo

Member
2002-11-11 6:52 am
da_madaxeman please, don't write about warez here, it's not the topic of this forum

Mr Evil: your white noise is -12dB, while mine (from spectralab) is -40dB. I thought this was normal, since a white noise is a signal containing every frequency. So a 0dB 100Hz, plus a 0dB 1kHz, plus a 0dB 359kHz .... would lead in something over 0dB (over full scale, not possible for a soundcard)
But now that I saw your attached file, all my theory seems wrong :bawling:
;)