Signal from noise [was: SUBharmonics, Relatedness and Euler]

Hey guys,

> >If you listen to a noise signal along with a copy that is delayed by 20ms
> >you will hear a 50Hz tone, where none exists.

(White) noise consists of all frequencies in equal mixture:

|
|
a|
m|----------------------
p|
|
|
|______________________
0 freq

Running a noise signal through 20ms delay will cause the signal present
which peaks every 20ms (that is, 50Hz) to be reinforced and thus
become twice as loud. The other frequencies are not so reinforced and
stay about the same. Another way of looking at it is to consider the
delay line as introducing a resonance at 50Hz.

So - voila! A magical tone from "nowhere".

- Jeff