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  • 1
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    Psychoacoustic considerations for helicopter noise quantification: Metrics, human response and criteria (1982)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-17
    Beschreibung: The purpose of this paper is to examine several aspects of helicopter noise quantification from the standpoint of psychoacoustics. Noise metrics in common use to describe far-field aircraft noise and the noise characteristics which they consider are discussed. Some findings of recent psychoacoustic research related specifically to helicopter noise quantification are presented. Criteria for the accuracy of noise metrics to quantify helicopter noise are discussed. Finally, the prospects for improved metrics and research needed to develop and validate improved metrics or existing metrics are discussed.
    Schlagwort(e): ACOUSTICS
    Materialart: Rotorcraft Noise; p 245-260
    Format: text
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  • 2
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    Human response to aircraft noise (1991)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The human auditory system and the perception of sound are discussed. The major concentration is on the annnoyance response and methods for relating the physical characteristics of sound to those psychosociological attributes associated with human response. Results selected from the extensive laboratory and field research conducted on human response to aircraft noise over the past several decades are presented along with discussions of the methodology commonly used in conducting that research. Finally, some of the more common criteria, regulations, and recommended practices for the control or limitation of aircraft noise are examined in light of the research findings on human response.
    Schlagwort(e): ACOUSTICS
    Materialart: Aeroacoustics of Flight Vehicles: Theory and Practice. Volume 2: Noise Control; p 1-52
    Format: application/pdf
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  • 3
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    Recent Langley helicopter acoustics contributions (1988)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The helicopter acoustics program at NASA Langley has included technology for elements of noise control ranging from sources of noise to receivers of noise. The scope of Langley contributions for about the last decade is discussed. Specifically, the resolution of two certification noise quantification issues by subjective acoustics research, the development status of the helicopter system noise prediction program ROTONET are reviewed and the highlights from research on blade rotational, broadband, and blade vortex interaction noise sources are presented. Finally, research contributions on helicopter cabin (or interior) noise control are presented. A bibliography of publications from the Langley helicopter acoustics program for the past 10 years is included.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA, Washington, NASA(Army Rotorcraft Technology. Volume 2: Materials and Structures, Propulsion and Drive Systems, Flight Dynamics and Control, and Acoustics; p 1003-1044
    Format: application/pdf
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  • 4
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    Noise transmission characteristics of advanced composite structural materials (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Previously cited in issue 10, p. 1473, Accession no. A83-25915
    Schlagwort(e): ACOUSTICS
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 528-535
    Format: text
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  • 5
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    Annoyance due to simulated blade-slap noise (1978)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The effects of several characteristics of blade slap noise on annoyance response were studied. These characteristics or parameters were the sound pressure level of the continuous noise used to simulate helicopter broadband noise, the ratio of impulse peak to broadband noise or crest factor, the number of pressure excursions comprising an impulse event, the rise and fall time of the individual impulses, and the repetition frequency of the impulses. Analyses were conducted to determine the correlation between subjective response and various physical measures for the range of parameters studied. A small but significant improvement in the predictive ability of PNL was provided by an A-weighted crest factor correlation. No significant improvement in predictive ability was provided by a rate correction.
    Schlagwort(e): ACOUSTICS
    Materialart: Helicopter Acoustics, Pt. 2; p 463-477
    Format: application/pdf
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  • 6
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    Supersonic jet noise - Its generation, prediction and effects on people and structures (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: This paper presents the results of a study aimed at quantifying the effects of jet source noise reduction, increases in aircraft lift, and reduced aircraft thrust on the take-off noise associated with supersonic civil transports. Supersonic jet noise sources are first described, and their frequency and directivity dependence are defined. The study utilizes NASA's Aircraft Noise Prediction Program in a parametric study to weigh the relative benefits of several approaches to low noise. The baseline aircraft concept used in these predictions is the AST-205-1 powered by GE21/J11-B14A scaled engines. Noise assessment is presented in terms of effective perceived noise levels at the FAA's centerline and sideline measuring locations for current subsonic aircraft, and in terms of audiologically perceived sound of people and other indirect effects. The results show that significant noise benefit can be achieved through proper understanding and utilization of all available approaches.
    Schlagwort(e): ACOUSTICS
    Materialart: SAE PAPER 901927
    Format: text
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  • 7
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    A feasibility study on the numerical modeling of interior noise fields (1986)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: New developments in electronics and computer control have made active methods of noise suppression feasible. To date, however, active methods of noise control have been applied principally in geometrically uniform spaces with localized sound sources. The purpose of this paper is to demonstrate how finite element techniques may be used to model sound fields and active control inside geometrically complex spaces with non-uniform acoustic boundaries and multiple spatially separated sources. A closed-form solution is derived for the case of a one-dimensional tube with a vibrating piston at each end. Results are compared with finite element solutions and the problem is then generalized to two-dimensions with non-uniform geometry and non-uniform acoustic boundaries.
    Schlagwort(e): ACOUSTICS
    Materialart: AIAA PAPER 86-1862
    Format: text
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  • 8
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    Status and capabilities of sonic boom simulators (1986)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The current status and capabilities of sonic boom simulators which might be used in future studies of the effects of sonic boom on people, animals, or structures is summarized. The list of candidate simulators is based on a literature search which was confined to the United States and Canada. Some of the simulators are fully operational, others could be made operational with a modest investment, and still others would require a major investment. For the sake of the completeness, some simulators which were the subject of a previous review, but which no longer exist, are also included herein.
    Schlagwort(e): ACOUSTICS
    Materialart: NASA-TM-87664 , NAS 1.15:87664
    Format: application/pdf
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  • 9
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    On the tones of round choked jets impinging on normal flat plates (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: An experimental investigation of the sound produced by an axisymmetric supersonic jet impinging on plates with variable size and nozzle-to-plate spacings was performed. Spectral analysis and schlieren photography were used to determine the sound characteristics and flow disturbances associated with the production of discrete tones. Two classes of tones, associated with small and large plates, existed for pressure ratios above 2.70. For lower pressure ratios, however, only large plate tones occurred for all plate sizes with choked jet screech appearing at the largest spacings. Reflector tests indicated that both classes of tones were part of a feedback loop to the nozzle. Schlieren photography revealed both symmetric and asymmetric disturbances in the large plate jet flows which corresponded to symmetrical and helical modes of oscillation in the cross-spectrum studies. In addition to this, both symmetric and asymmetric oscillations of the shock waves occurred in the large plate case while symmetric oscillations of the shock wave occurred in the small plate case.
    Schlagwort(e): ACOUSTICS
    Materialart: AIAA PAPER 90-3985
    Format: text
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  • 10
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    Acoustic testing of high temperature panels (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Results are presented of a series of thermal-acoustic tests conducted on the NASA Langley Research Center Thermal-Acoustic Test Apparatus to (1) investigate techniques for obtaining strain measurements on metallic and carbon-carbon materials at elevated temperature; (2) document the dynamic strain response characteristics of several superalloy honeycomb thermal protection system panels at elevated temperatures of up to 1200 F; and (3) determine the strain response and sonic fatigue behavior of four carbon-carbon panels at both ambient and elevated temperatures. A second study tested four carbon-carbon panels to document panel dynamic response characteristics at ambient and elevated temperature, determine time to failure and faliure modes, and collect continuous strain data up to panel failure. Strain data are presented from both types of panels, and problems encountered in obtaining reliable strain data on the carbon-carbon panels are described. The failure modes of the carbon-carbon panels are examined.
    Schlagwort(e): ACOUSTICS
    Materialart: AIAA PAPER 90-3939
    Format: text
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