(... as Za sneaks up with a hand-held airhorn...)
I was reading through those two fascinating links that Za posted and was interested to read that acoustic locaters were deployed well into World War II in order to deceive the Germans and hide the fact that the Allies were, in fact, using radar.
(... 1940's rope-a-dope..... float like a butterfly.... sting like a bee!...)
.... no wonder we won......
-whatever
-Lou