In message <19961217205812679.AAC279@rush.u-netsys.com.br>, Engenharia
Mestra de Sistemas Sociedade Ltda <mestra@U-NETSYS.COM.BR> writes
>Hi, folks:
>
>I am trying to find some information about noise cancelling techniques, like
>adding symmetrical waves, etc.
>
>Does anyone know where I can find this ?
>
>
>TIA,
>
>
>Pedro Drummond.

Try the comp.dsp newsgroup, this comes up all the time there. If you
find where postings are archived, you should be able to get hold of lots
of stuff.

--
Leon Heller