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  • 1
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    The effect of operations on the ground noise footprints associated with a large multibladed, nonbanging helicopter (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In order to expand the data base of helicopter external noise characteristics, a flyover noise measurement program was conducted utilizing the NASA Civil Helicopter Research Aircraft. The remotely operated multiple array acoustics range (ROMAAR) and a 2560-m linear microphone array were utilized for the purpose of documenting the noise characteristics of the test helicopter during flyby and landing operations. By utilizing both ROMAAR concept and the linear array, the data necessary to plot the ground noise footprints and noise radiation patterns were obtained. Examples of the measured noise signature of the test helicopter, the ground noise footprint or contours, and the directivity patterns measured during level flyby and landing operations of a large, multibladed, nonbanging helicopter, the CH-53, are presented.
    Keywords: ACOUSTICS
    Type: Helicopter Acoustics, Pt. 2; p 519-533
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Observed variability of aircraft noise footprint measurements (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A description is presented of some measurements which illustrate the variability of the experimentally developed ground noise footprints for a series of landing approach operations of a turbojet aircraft and a turbine powered helicopter. Measurements on the recently developed NASA Remotely Operated Multiple Array Acoustic Range are considered. The information presented is related to a turbojet fighter aircraft and a turbine powered helicopter performing landing approach operations along a 3 deg approach path. Each vehicle was acquired on radar tracking approximately 10 kilometers from the touchdown point and entered the test area at an altitude of about 470 m. The measured variations in meteorological quantities for the two time periods during which these tests were conducted are presented in graphs. Other graphs show the ground noise contour for the turbojet aircraft and the turbine helicopter.
    Keywords: ACOUSTICS
    Type: In: NOISE-CON 77; National Conference on Noise Control Engineering; Oct 17, 1977 - Oct 19, 1977; Hampton, VA
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    A research program to reduce interior noise in general aviation airplanes (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The relevance of KU-FRL test results in predicting (theoretically or semi-empirically) interior noise levels in general aviation aircraft was studied. As a result of this study, it was decided to make a few additions to the program. These additions are: (1) to use three (instead of two) noise sources in the plane wave tube to evaluate the influence of excitation spectrum on panel response, (2) to use theoretical and experimental data obtained in the course of the project to develop more efficient noise reduction materials (or procedures to apply these), or to develop guidelines for the design of such materials for procedures, and (3) to use nonstructural materials in the collection of specimens to be tested in the KU-FRL plane wave tube.
    Keywords: ACOUSTICS
    Type: NASA-CR-153268 , KU-FRL-317-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    A research program to reduce interior noise in general aviation airplanes. Design of an acoustic panel test facility (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The design, construction, and costs of a test facility for determining the sound transmission loss characteristics of various panels and panel treatments are described. The pressurization system and electronic equipment used in experimental testing are discussed as well as the reliability of the facility and the data gathered. Tests results are compared to pertinent acoustical theories for panel behavior and minor anomalies in the data are examined. A method for predicting panel behavior in the stiffness region is also presented.
    Keywords: ACOUSTICS
    Type: NASA-CR-155152 , KU-FRL-317-3
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Unsteady stator response to upstream rotor wakes (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The results are presented of an investigation of the unsteady pressures generated on a stator due to its interaction with the wakes shed by an upstream rotor. The influence of stator solidity, incidence flow angle and rotor/stator spacing are discussed. The results show that the major influence is due to stator solidity, particularly at large values of incidence angle. Comparisons of the measured data with an existing unsteady cascade analysis show similar trends in the chordwise variation of the predicted and measured unsteady pressure difference across the blades. Comparisons with an isolated airfoil analysis indicate the influence of solidity and unsteady blade-to-blade interaction. All comparisons were conducted for an incompressible flow with a reduced frequency of approximately 5.0.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 79-0579 , American Institute of Aeronautics and Astronautics, Aeroacoustics Conference; Mar 12, 1979 - Mar 14, 1979; Seattle, WA
    Format: text
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    NASA TECHNICAL REPORTS
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