Re: REFLECTOR: Door Trim Sealing

[HadleyAir@aol.com]

In a message dated 7/26/99 6:01:41 PM Eastern Daylight Time, jcbarnes@ibm.net 
writes:

>  I tested both Lightspeeds at SNF and found them very quiet (I had to 
strain to hear
>  the TORA TORA TORA airshow bombs going on outside -- felt those more than 
heard them),          >  comfortable, light, and had great CD stereo 
reproduction at both ends of the spectrum.

Jeff (and all), 

IMHO, your testimony demostrates the one negative aspect of ANR systems. Most 
ANR systems are designed to detect and cancel repeditive audio signals of 
similar frequency and amplitude and/or rapid increases of amplitude (volume), 
such as your "TORA TORA TORA" bombs.

These detected noises include for example, wind noise, the 'drone' of the 
engine, repeating rod knocks, etc. OOPS! Did I say "rod knocks"? 

The Collins Foundation, owners and operators of the B-24 Liberator "All 
American" and B-17 "909" were donated sets of a major leading manufacturers' 
ANR headsets.
The boys flying the B-24 did not hear a rod knocking in the #4 engine until 
they were alerted to a red flashing LOW OIL PRESS light on the panel. Those 
$900 headsets cost the foundation $68K in engine repairs.   They have since 
gone back to the old David Clarks. 

I sincerely am a believer in ANR systems. Saving ones hearing should not be 
taken lightly. But having first hand knowledge of an instance such as this 
leads me to the old adage that "too much of a good thing may not be good"! 

With a rear mounted engine, what we don't hear may just be something that we 
really want to be able to listen to. This is just something to think about 
when considering "quality" ANR headsets. 

IMHO

Martin