[sdiy] Noise as one unsteady tone!

[Magnus Danielson]

From: "Fredrik Carlqvist" <Fredrik.Carlqvist at iar.se>
Subject: RE: [sdiy] Noise as one unsteady tone!
Date: Mon, 5 Sep 2005 10:14:06 +0200
Message-ID: <031614A0C3206A4192CC39A42A33D3F60A2F60 at seupp-srv-email.ad.iar.com>

> 
> If you go to the frequency domain (fourier transform and such), the
> noise looks the same and is therefore said to contain all frequencies.
> There is power in all frequency bands. This does not mean there are any
> tones in it. 

If you have a very selective filter you will find an unstable "tone" anywhere
you look, but what you hear is nothing but a narrow filter stimulated by noise
and not a characteristic of the noise itself. Not that it is not usefull, but
it is a different matter.

> If you have a narrow band pass filter, it will find energy no matter
> where you set the center frequency when the input is white noise. This
> way you can have something that sounds like a tone, but with an unstable
> level.

It depends on your averaging time naturally.

Cheers,
Magnus

> Fredrik C
> 
> 
> > -----Original Message-----
> > From: owner-synth-diy at dropmix.xs4all.nl 
> > [mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of karl dalen
> > Sent: den 5 september 2005 03:19
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: [sdiy] Noise as one unsteady tone!
> > 
> > Tip!
> > 
> > Some time ago i was looking for a low voltage noise source,
> > and by coincidence i have found one. As we know its difficult
> > to do a analog withe noise generator at low voltages by using 
> > the typical PN junction, zener or diode couppled.
> > 
> > But i came by the korg Poly 800 and it uses a simple 
> > NPN, open collector, emitter to +V, base negative biased
> > to -5V, AC coupled to a simple inverter stage. It works verry
> > well even at supply volatges of  +/-3,5. I use it with +/-5 volt
> > and a non selected BC547 and a 2,2M ohm gain stage wich 
> > gives several volts of uniform with noise.
> > 
> > Splendid!
> > 
> > Speaking of noise, theory says that white gaussian
> > noise contains all frequencies but are theese steady
> > tones or are they random in frequency?
> > Or is it "one" wave with its frequency randomly?
> > 
> > KD 
> > 
>