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Jet Noise Reduction Potential From Emerging Variable Cycle Technologies

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01-08-2013, 04:22 PM
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LadyStanley
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Jet Noise Reduction Potential From Emerging Variable Cycle Technologies

http://ntrs.nasa.gov/search.jsp?R=20...?R=20130000450

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Acoustic and flow-field experiments were conducted on exhaust concepts for the next generation supersonic, commercial aircraft. The concepts were developed by Lockheed Martin (LM), Rolls-Royce Liberty Works (RRLW), and General Electric Global Research (GEGR) as part of an N+2 (next generation forward) aircraft system study initiated by the Supersonics Project in NASA s Fundamental Aeronautics Program. The experiments were conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center. The exhaust concepts utilized ejectors, inverted velocity profiles, and fluidic shields. One of the ejector concepts was found to produce stagnant flow within the ejector and the other ejector concept produced discrete-frequency tones that degraded the acoustic performance of the model. The concept incorporating an inverted velocity profile and fluid shield produced overall-sound-pressure-level reductions of 6 dB relative to a single stream nozzle at the peak jet noise angle for some nozzle pressure ratios. Flow separations in the nozzle degraded the acoustic performance of the inverted velocity profile model at low nozzle pressure ratios.

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01-09-2013, 10:39 AM
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Bocephus86
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I understood 3 words in that text. That stuff is so interesting I should have studied engineering or physics in college instead of business.

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01-10-2013, 09:06 AM
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Tom Polakis
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Originally Posted by Bocephus86 View Post
I understood 3 words in that text. That stuff is so interesting I should have studied engineering or physics in college instead of business.
I don't know if I should be embarrassed or proud to state that I understood almost all of it. I'm a career aircraft engine engineer. As such, I was disappointed to read all of that to finally learn that the sound is reduced by a miniscule 6 dB. That would be a perceptible reduction in the roar of the engine, but not nearly enough to allow aircraft to take off over residential corridors without complaints.

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01-10-2013, 01:32 PM
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considering a whisper is around 30-40 db, that's a whole lot of effort for saving the equivalent of a fart in a noisy room.

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01-10-2013, 02:17 PM
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Aerolanche
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Originally Posted by Richer's Ghost View Post
considering a whisper is around 30-40 db, that's a whole lot of effort for saving the equivalent of a fart in a noisy room.
I don't think that's the right way to look at it.

For a 6 dB reduction, wouldn't that mean the amplitude of the sound waves would be cut in half?

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01-10-2013, 03:19 PM
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Originally Posted by Aerolanche View Post
I don't think that's the right way to look at it.

For a 6 dB reduction, wouldn't that mean the amplitude of the sound waves would be cut in half?
Ok, it says pressure levels, not direct acoustic levels. The title of noise reduction threw me off.

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