Sound command query.

I have a question about Sound command.

How sound command generate white noise, for example with note 255 ?
Note 1 to 127 are 78.74Hz to 9.999.98 Hz.
Note 128 to 255 ?

How can i recreate note 255 with this :
http://www.picbasic.co.uk/forum/showthread.php?t=535 ?

Thank you!