Re: identifying engines by sound

From:         Steve Lacker <slacker@arlut.utexas.edu>
Organization: applied research laboratories
Date:         06 Sep 95 01:04:11 
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Other interesting engine sounds I've noted in my travels:

JT-8d: (not the -200 series) A distinctive wail (almost like a grinding wheel
on sheet metal) during taxi/ground operations which fades as the engine
accelerates to takeoff thrust (I've been told that this sound is due to inlet
guide vane spacing, which is why the guide spacing is often changed as part of
a hush-kit).

JT-3d: Unmistakeable whistling wail during descent.

J-57: Loud loud loud!! (and smoky). The sound of a J-57 KC-135 (or better yet,
a B-52) taking off should be experienced by everyone at least once.

CFM-56 (and other high-bypass powerplants): Listen to a plane as it lines up
for takeoff. If the pilot advances the throttle quickly, there is a surge of
very loud sound which then subsides as the engine spools up. I presume this is
because the engine core airflow (the noisiest part) responds first, before the
fan airflow (which shrouds and muffles the core flow) picks up enough to mask
the core noise.

--
Steve Lacker	/	Applied Research Laboratories, The University of Texas
512-835-3286	/	PO Box 8029, Austin TX 78713-8029
slacker@arlut.utexas.edu