Subject: Sound: Math, Physics and Conservation (LFAS noise levels) (fwd)

Mike Williamson (
Fri, 11 Dec 1998 10:29:46 -0500 (EST)

---------- Forwarded message ----------
Date: Thu, 10 Dec 1998 23:17:35 +0000
From: Lee Tepley <>
To: pita@sun.SIMMONS.EDU
Subject: LFAS noise levels

This e-mail is being distributed to inform interested parties of a
simple analysis that I did which demonstrates that the Navy is
misleading the public (probably intentionally) about the underwater
sound level of Low Frequency Active Sonar (LFAS).

It would have been nice if I could have done this while the Hawaii tests
were still underway but hopefully now is still =93better late than never=94=

My analysis is based on a statement made by the Navy in one or more of
their reports on LFAS which was often quoted by National Marine
Fisheries Service to help justify their support of the LFAS test program
in Hawaii. A similar statement can presently be found under =93Debunking
the Myths=94 on the Navy LFAS web site at

The important part of the statement is: =93The acoustic power of a jet at
take off (180 dB air) will generate about 100 kilowatts.  The acoustic
power of the LFA speaker (200 dB water) would generate about 1 kilowatt
or the equivalent of 1% of the sound level of a jet engine.  In other
words, a jet engine is 100 times louder than a 200 decibel sound in

I was suspicious of the accuracy of this statement when I first saw it.
Recently I was able to follow through some simple mathematics from which
it was clear that the LFA speaker underwater was, in fact, louder than
the hypothetical jet engine.  The details of the analysis are given on
my almost identical websites at:

The analysis was based on the basic physics of the behavior of sound
waves in air and water.  It is hard to believe that the Navy project
scientists were unaware of these facts.  Hence it seems that the Navy=92s
statement was deliberately misleading.

Feel free to copy any or all of the analysis and use it on other


Lee Tepley