On Sun, 24 Jan 2010 14:41:09 +0100, "Edgar"
wrote:


"Bruce In Bangkok" wrote in message
.
snipped
.
Which does not mention the electronic method which makes one wonder
about the validity of the claims for the "sound system".

I seem to recall that this system was based on observations which showed
that the transponders of echo sounders remain free from fouling.

Transducers convert electricity to sound, in this case. Which is what
your meant. Transponders pick up an signal and send out a reply. They
have them in comsats. IFF uses transponders.

Casady