[sdiy] Noise as one unsteady tone!

[Richard Wentk]

At 12:07 05/09/2005, Magnus Danielson wrote:

>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.

This is one of those times where theory collides with the real world.

In reality if you patch together enough sine oscillators - like a few 
thousand - spread randomly across the frequency band, you get a reasonable 
approximation of noise.

If you randomly vary their amplitudes you get a much quieter signal that 
also sounds like noise.

So technically all you can say about noise is that the power spectrum has a 
certain shape. A time domain recipe for the component frequencies that 
create that shape isn't necessarily clearly defined.

Richard