Re: Engine noise question

Date:         08 Dec 96 04:12:38 
From:         Michael McEvilley <mmcevill@mitretek.org>
Organization: Mitretek Systems
References:   1 2 3 4
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b17864@vaxc.phx1.aro.allied.com wrote:
>
> In article <airliners.1996.2590@ohare.Chicago.COM>, kls@ohare.Chicago.COM (Karl Swartz) writes:
> > In article <airliners.1996.2589@ohare.Chicago.COM>, faurecm@halcyon.com (C. Marin Faure) wrote:
> >>The "snarl" or "buzz" you hear from a large plane like a 747, 777,
> >>MD-11, etc. as they take off is really the fan noise, not the jet
> >>core noise, which is the roar part.
>
> There are a number of theories around regarding fan buzz (that buzz saw
> wail you hear on some engines). The one that I tend to believe is that it
> is due to the vortex from the blade tip or the mid span damper (more
> likely) hitting the downstream vanes ...

> Mark Johnston
> Sr. Development Specialist
> Military Engine Enterprise
> AlliedSignal Engines

Saw the 'military' in your sig, and just wanted to mention...
Although not airliners, 've noted during the years spent in the Air
Force that C5s were notorious for the 'snarling' sound during takeoff,
whereas C141s made a very distinctive whining sound.

-michael

--
Michael A. McEvilley
Mitretek Systems
mmcevill@mitretek.org
703-610-1665 (voice)
703-610-1699 (fax)