In Flight Far Field Measurement Of Helicopter Impulsive Noise PDF Download
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Total Pages | : 15 |
Release | : 1976 |
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Download In-Flight Far-Field Measurement of Helicopter Impulsive Noise Book in PDF, ePub and Kindle
An in-flight technique for measuring UH-1H helicopter impulsive noise (sometimes called 'blade slap') by stationkeeping with a quiet instrumented lead aircraft was found to be highly successful. Far-field quantitative acoustic waveforms and radiation patterns were easily obtained over a wide, continuous range of UH-1H flight conditions, including several areas known to produce annoying acoustic radiation. The data collected using this technique were not (to any significant degree) contaminated by transmission path distortions that have hindered measurement efforts in the past. The two major finding of this initial measurement program were: (1) Judging the occurrence and severity of a helicopter's radiated impulsive noise signature from cabin-based noise measurements can be misleading. For the UH-1H helicopter, reduction in cabin audible impulsive noise levels may constitute a necessary but certainly not sufficient to indicate that far-field impulsive noise radiation has been reduced. The following three distinct types of impulsive noise are radiated by the Un-1H helicopter while flying between 80 and 115 knots at descent rates from zero to 1000 ft/min: (a) A series of positive pressure pulses believed to be related to blade-tip vortex interaction. These pulses are responsible for the crisp popping sound of the radiated noise; (b) A negative pressure disturbance that rapidly increases in amplitude with forward velocity, becoming quite intense and sawtoothed in shape at 115 knots IAS; and (c) A narrow positive pressure spike that closely follows that sawtooth-shaped negative pressure pulse at high airspeeds (115 knots).
Author | : F. H. Schmitz |
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Total Pages | : 110 |
Release | : 1983 |
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Download Helicopter Impulsive Noise: Theoretical and Experimental Status Book in PDF, ePub and Kindle
The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
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Total Pages | : 24 |
Release | : 1987 |
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Download Helicopter Main-rotor Speed Effects on Far-field Acoustic Levels Book in PDF, ePub and Kindle
Author | : Clemans A. Powell |
Publisher | : |
Total Pages | : 48 |
Release | : 1981 |
Genre | : Helicopters |
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Download Subjective Field Study of Response to Impulsive Helicopter Noise Book in PDF, ePub and Kindle
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Total Pages | : 368 |
Release | : 1988 |
Genre | : Astronautics |
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Download NASA Technical Paper Book in PDF, ePub and Kindle
Author | : United States. National Aeronautics and Space Administration |
Publisher | : |
Total Pages | : 256 |
Release | : 1988 |
Genre | : Aeronautics |
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Download NASA Technical Paper Book in PDF, ePub and Kindle
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Total Pages | : 772 |
Release | : 1994 |
Genre | : Aeronautics |
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Download Scientific and Technical Aerospace Reports Book in PDF, ePub and Kindle
Author | : Wayne Johnson |
Publisher | : Courier Corporation |
Total Pages | : 1122 |
Release | : 2012-03-07 |
Genre | : Technology & Engineering |
ISBN | : 0486131823 |
Download Helicopter Theory Book in PDF, ePub and Kindle
Monumental engineering text covers vertical flight, forward flight, performance, mathematics of rotating systems, rotary wing dynamics and aerodynamics, aeroelasticity, stability and control, stall, noise, and more. 189 illustrations. 1980 edition.
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Total Pages | : 40 |
Release | : 1983 |
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Download Model Helicopter Rotor High-speed Impulsive Noise: Measured Acoustics and Blade Pressures Book in PDF, ePub and Kindle
Author | : Harvey H. Hubbard |
Publisher | : |
Total Pages | : 616 |
Release | : 1991 |
Genre | : Aerodynamic noise |
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Download Aeroacoustics of Flight Vehicles Book in PDF, ePub and Kindle