Hi Richard, thanks for joining the discussion, read below...

Richard Lamb wrote in message ...
SHOCK waves, not sine waves.

Any periodic signal (or sound) can be thought of as an infinite sum of
the harmonics of the fundamental. Even complicated waveforms.

and more harmonics than a '60's rock band!

Yup, lots of harmonics, each one containing its portion of the sound
power. The higher the harmonic, the less power it generally contains.

AND, to make it work, they ALL have to be exactly
(there's the E word)
and perfectly
(the P word too)

(I _could add Absolutely and score 3 for 3!)

180 out of phase?

Its really a matter of degrees (pun intended), the closer to 180 you
get, the better the cancelation, but its not an all or nothing kind of
thing. For example, a 170/190 degree phase shift cancels 98%.