#1552, WWII History, and Foote

Ed:

I like the comment on beat phenomenon and airplane
engines out of synch.

I have heard that a major fallacy of the Germans in WWII was their
staunch refusal to synchronize their bombers' engines.

The result, of course, was that beats could be heard halfway
around the world! Thus always signalling the planes' arrival!

Rick Sanford
New York City

------------------------------

End of TUNING Digest 1544
*************************

On Tue, 6 Oct 1998, Kraig Grady wrote:

> By the way the beat canceling idea kind of goes with stockhausen idea of
> a "Sonic Trash can" a device that produces the inverse wave causing
> silence! don't hold your breath!

Ah yes, 'black noise'

The fundamental problem with a black noise generator is that unless the
wavelength of the sound being cancelled out in the air is significantly
greater than the distance between the sound source and the black noise
source, it produces an interference pattern rather than simply cancelling
out.

Cancelling beats has much the same problem, my solution is to play
everything out of one speaker, in which case the distance between the
cancelling source and the beating source is zero (unless you get into the
distance between the woofer and the tweeter, which I'm *hoping* won't
become a problem.) I suspect it's just plain impossible to get that sort
of effect out of normal acoustic instruments.

I'm now buying the two books people mentioned, and will hopefully be able
to work out some formulas after reading through them. The main thing I'm
still unclear on at the moment is how to compute volume, although at the
moment I suspect it's based on the integral of the square of the second
derivative of f(x). Hopefully I'll know for sure after doing my homework.

-Bram

------------------------------

End of TUNING Digest 1546
*************************