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This report is a compilation of publications from acoustics research at the Langley Research Center. The reports listed are in chronological order and summarize the research output of the Acoustics Division for the period January ...
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This report is a compilation of publications from acoustics research at the Langley Research Center. The reports listed are in chronological order and summarize the research output of the Acoustics Division for the period January 1987 - September 1992.
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A systematic experimental program was conducted to develop a data base for the noise and related flow characteristics of upper surface blown configurations. The effect of various geometric and flow parameters was investigated expe...
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A systematic experimental program was conducted to develop a data base for the noise and related flow characteristics of upper surface blown configurations. The effect of various geometric and flow parameters was investigated experimentally. The dominant noise was identified from the measured flow and noise characteristics to be generated downstream of the trailing edge. The possibilities of noise reduction techniques were explored. A USB noise prediction program was developed empirically to calculate noise levels at any point and noise contours (footprints). Using this noise predic¬tion program, and the cruise performance data base from NASA Contract NAS1-13871, aircraft design studies were conducted to integrate low noise and good performance characteristics. A theory was developed for the noise from the highly sheared layer of a trailing edge wake. Theoretical results compare favorably with the measured noise of the USB model.
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In 1986 New Jersey completed an eight-mile section of I-78 in Union County, whichincluded the construction of two innovative traffic noise barriers. Both barriers were concrete and post-and-panel structures, designed ostensibly to...
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In 1986 New Jersey completed an eight-mile section of I-78 in Union County, whichincluded the construction of two innovative traffic noise barriers. Both barriers were concrete and post-and-panel structures, designed ostensibly to reduce the assumed interaction between parallel barriers which was considered to degrade barrier effectiveness. One barrier was tilted 10 degrees away from the roadway and had a standard hard concrete grapestake finish, the opposite barrier being of the same type. The second type of barrier was vertical and the panels were covered with a proprietary absorbing finish. Some of the opposite barriers had the same finish, while others had a non-absorbing finish. Both innovative barriers were evaluated for their effectiveness in reducing farside noise levels and increasing nearside insertion loss vis-a-vis a standard barrier with a reflective finish. This evaluation was carried out in two phases.
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A two-year comprehensive program on fan and compressor noise was undertaken by Pratt & Whitney Aircraft under contract to the Federal Aviation Administration. The primary objective of the contract was the development of an accurate prediction system, based on theoretical concepts and/or empirical data, which would enable the selection of proper acoustical design choices for future engines. Experimental programs were conducted using a variety of test rigs to provide acoustic data and to validate theoretical concepts. Mathematical models were developed for each type of fan noise, and their applicability to actual engines was evaluated. Although more work is need to reduce further the contribution of fan and compressor noise to the total noise levels of future engines, the material presented herein represents significant progress in the understanding of particular noise-generating mechanisms and the capability to predict fan noise....
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A two-year comprehensive program on fan and compressor noise was undertaken by Pratt & Whitney Aircraft under contract to the Federal Aviation Administration. The primary objective of the contract was the development of an accurate prediction system, based on theoretical concepts and/or empirical data, which would enable the selection of proper acoustical design choices for future engines. Experimental programs were conducted using a variety of test rigs to provide acoustic data and to validate theoretical concepts. Mathematical models were developed for each type of fan noise, and their applicability to actual engines was evaluated. Although more work is need to reduce further the contribution of fan and compressor noise to the total noise levels of future engines, the material presented herein represents significant progress in the understanding of particular noise-generating mechanisms and the capability to predict fan noise.
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Externally blown flap models were tested for noise and performance at one-fifth scale in a static facility and at one-tenth scale in a large acoustically-treated wind tunnel. The static tests covered two flap designs, conical and ...
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Externally blown flap models were tested for noise and performance at one-fifth scale in a static facility and at one-tenth scale in a large acoustically-treated wind tunnel. The static tests covered two flap designs, conical and ejector nozzles, third-flap noise-reduction treatments, internal blowing, and flap/nozzle geometry variations. The wind tunnel variables wave triple-slotted or single-slotted flaps, sweep angle, and solid or performed third flap.
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Maximum observed noise levels in terms of dBA are presented for four typical small propeller-driven airplanes. The data are derived from the results of in-flight noise recordings taken by the Faculty of Aerospace Engineering of De...
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Maximum observed noise levels in terms of dBA are presented for four typical small propeller-driven airplanes. The data are derived from the results of in-flight noise recordings taken by the Faculty of Aerospace Engineering of Delft University of Technology. Maximum levels versus distance as a function of powersetting are given wherever possible.
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The fourth in a series of NASA/SAE Interior Noise Workshops was held on May 19 and 20, 1992. The theme of the workshop was new technology and applications for aircraft noise with emphasis on source noise prediction; cabin noise pr...
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The fourth in a series of NASA/SAE Interior Noise Workshops was held on May 19 and 20, 1992. The theme of the workshop was new technology and applications for aircraft noise with emphasis on source noise prediction; cabin noise prediction; cabin noise control, including active and passive methods; and cabin interior noise procedures. This report is a compilation of the presentations made at the meeting which addressed the above issues.
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This report is one of a series describing the research program undertaken by the Aerospace Medical Research Laboratory to develop procedures for predicting community noise exposure resulting from aircraft operations. This report o...
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This report is one of a series describing the research program undertaken by the Aerospace Medical Research Laboratory to develop procedures for predicting community noise exposure resulting from aircraft operations. This report outlines the acoustic measurement test conditions, the acoustic data reduction and interpretation procedures, and the type of aircraft performance information needed to obtain a noise data file for predicting the noise produced by aircraft operations. The procedures result in the descriptions of the noise of an aircraft in terms of the effective perceived noise level, the sound exposure level and several other noise measures. Level flight measurements and static engine noise tests are described, and are applicable to conventional fixed wing aircraft and helicopters.
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