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  • 1
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    Capabilities of the thermal acoustic fatigue apparatus (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Thermal Acoustic Fatigue Apparatus (TAFA) is a facility for applying intense noise and heat to small test panels. Modifications to TAFA have increased the heating capability to 44 BTU/(ft.-sec.), making it possible to heat test panels to 2000 F and concurrently apply 168 dB of noise. Results of acoustic and thermal surveys are shown. Two test items, a 0.09 in. steel panel and an insulated panel, were used in the thermal survey.
    Keywords: ACOUSTICS
    Type: NASA-TM-104106 , NAS 1.15:104106
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Structureborne noise in aircraft: Modal tests (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: As part of an investigation to develop measurement techniques for structureborne noise, three modal surveys have been conducted on an OV-10A aircraft and the results have been presented. The purpose of the modal surveys was to identify suitable locations for mounting accelerometer and strain gages in subsequent tests in which transfer functions relating wing vibration to interior noise were to be determined. These surveys are as follows:(1) wing/fuselage modal survey utilizing one shaker under the right wing; (2) complete wing modal survey utilizing two shakers, one under each wing; and (3) fuselage side panel modal survey utilizing a small instrumented hammer. The predominant frequencies and damping ratios for each analysis were listed in tables. The primary mode shapes at the lower frequencies and at frequencies near the expected engine driving frequencies have been shown for each survey.
    Keywords: ACOUSTICS
    Type: NASA-TM-87739 , NAS 1.15:87739 , USAAVSCOM-TM-86-B-3
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Interior noise and vibration measurements on operational military helicopters and comparisons with various ride quality criteria (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The results of physical measurements of the interior noise and vibration obtained within eight operational military helicopters are presented. The data were extensively analyzed and are presented in the following forms: noise and vibration spectra, overall root-mean-square acceleration levels in three linear axes, peak accelerations at dominant blade passage frequencies, acceleration exceedance data, and overall and ""A'' weighted sound pressure levels. Peak acceleration levels were compared to the ISO 1-hr reduced comfort and fatigue decreased proficiency boundaries and the NASA discomfort criteria. The ""A'' weighted noise levels were compared to the NASA annoyance criteria, and the overall noise spectra were compared to MIL-STD-1294 (""Acoustical Noise Limits in Helicopters''). Specific vibration components at blade passage frequencies for several aircraft exceeded both the ISO reduced comfort boundary and the NASA passenger discomfort criteria. The ""A'' weighted noise levels, corrected for SPH-4 helmet attenuation characteristics, exceeded the NASA annoyance threshold for several aircraft.
    Keywords: ACOUSTICS
    Type: NASA-TM-84664 , L-15598 , NAS 1.15:84664 , AVRADCOM-TR-83-D-21 , AD-A132102
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    The development of interior noise and vibration criteria (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: A generalized model was developed for estimating passenger discomfort response to combined noise and vibration. This model accounts for broadband noise and vibration spectra and multiple axes of vibration as well as the interactive effects of combined noise and vibration. The model has the unique capability of transforming individual components of noise/vibration environment into subjective comfort units and then combining these comfort units to produce a total index of passenger discomfort and useful sub-indices that typify passenger comfort within the environment. An overview of the model development is presented including the methodology employed, major elements of the model, model applications, and a brief description of a commercially available portable ride comfort meter based directly upon the model algorithms. Also discussed are potential criteria formats that account for the interactive effects of noise and vibration on human discomfort response.
    Keywords: ACOUSTICS
    Type: NASA-TM-102736 , NAS 1.15:102736 , International Symposium on Subjective Responses Under Simultaneous Exposures to Noise and Vibration; Jun 06, 1990 - Jun 08, 1990; Tampere; Finland*United States|26-30 Nov. 1990jun26-30 Nov. 1990; San Diego, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Interior noise reduction in a large civil helicopter (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of an evaluation of the effectiveness of current noise reduction technology in attaining acceptable levels of interior noise in a large (about 20,000 kg) passenger-carrying helicopter are presented. The helicopter studied is a modified CH-53A with a specially designed, acoustically treated passenger cabin. The acoustic treatment reduced the average A-weighted interior noise levels from 115 db to 87 db. The study suggests selected improvements in the acoustic treatment which could result in additional reduction in cabin noise levels. The resulting levels would be only slightly greater than the interior noise levels of current narrow-body jet transports.
    Keywords: ACOUSTICS
    Type: NASA-TN-D-8477 , L-11349
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Time-of-day Corrections to Aircraft Noise Metrics (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The historical and background aspects of time-of-day corrections as well as the evidence supporting these corrections are discussed. Health, welfare, and economic impacts, needs a criteria, and government policy and regulation, are also reported.
    Keywords: ACOUSTICS
    Type: NASA-CP-2135 , FAA-EE-80-3 , L-13779 , Mar 11, 1980 - Mar 12, 1980; Hampton, VA; United States
    Format: application/pdf
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