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Calculation procedures are presented for predicting maximum passby noise levels and contours (footprints) of conventional jet aircraft with or without noise suppression devices. The procedures have been computerized and a user's g...
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Calculation procedures are presented for predicting maximum passby noise levels and contours (footprints) of conventional jet aircraft with or without noise suppression devices. The procedures have been computerized and a user's guide is presented for the computer programs to be used in predicting the noise characteristics during aircraft takeoffs, fly-over, and/or landing operations.
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A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends...
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A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound power level agreed well with measurements from tests conducted in 2007 in the NASA Glenn Advanced Noise Control Fan. Calculated values of sound power levels radiated upstream were demonstrated to be sensitive to the accuracy of the modeled wakes from the cylindrical rods that were placed upstream of the fan to distort the inflow. Results indicate a continued need to obtain accurate aerodynamic predictions and measurements at the fan inlet plane as engineers work towards developing fan inflow distortion tone noise prediction tools.
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The acoustic assessment task for both the Subsonic Fixed Wing and the Supersonic projects under NASA s Fundamental Aeronautics Program was designed to assess the current state-of-the-art in noise prediction capability and to estab...
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The acoustic assessment task for both the Subsonic Fixed Wing and the Supersonic projects under NASA s Fundamental Aeronautics Program was designed to assess the current state-of-the-art in noise prediction capability and to establish baselines for gauging future progress. The documentation of our current capabilities included quantifying the differences between predictions of noise from computer codes and measurements of noise from experimental tests. Quantifying the accuracy of both the computed and experimental results further enhanced the credibility of the assessment. This presentation gives sample results from codes representative of NASA s capabilities in aircraft noise prediction at the system level and at the component level. These include semi-empirical, statistical, analytical, and numerical codes. An example of system level results is shown for an aircraft. Component level results are shown for airframe flaps and landing gear, for jet noise from a variety of nozzles, and for broadband fan noise. Additional results are shown for modeling of the acoustic behavior of duct acoustic lining and the attenuation of sound in lined ducts with flow.
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Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integr...
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Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integrated Noise Model. Several thrust prediction techniques were evaluated. Measured sound exposure levels for departure operations were found to be 4 to 10 dB higher than predicted, depending on the thrust prediction technique employed. Differences between measured and predicted levels are shown to be related to atmospheric conditions present at the aircraft altitude.
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摘要 :
Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integr...
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Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integrated Noise Model. Several thrust prediction techniques were evaluated. Measured sound exposure levels for departure operations were found to be 4 to 10 dB higher than predicted, depending on the thrust prediction technique employed. Differences between measured and predicted levels are shown to be related to atmospheric conditions present at the aircraft altitude.
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摘要 :
Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integr...
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Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integrated Noise Model. Several thrust prediction techniques were evaluated. Measured sound exposure levels for departure operations were found to be 4 to 10 dB higher than predicted, depending on the thrust prediction technique employed. Differences between measured and predicted levels are shown to be related to atmospheric conditions present at the aircraft altitude.
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The current understanding and methods of prediction of airframe noise, defined as the noise generated by an aircraft in flight in the absence of power, is assessed. Approaches to predictions relying upon flyover data and component...
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The current understanding and methods of prediction of airframe noise, defined as the noise generated by an aircraft in flight in the absence of power, is assessed. Approaches to predictions relying upon flyover data and component theoretical analyses are developed. In addition, areas where further research is required are identified.
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This document describes an ambient noise measurement protocol, a detailed methodology for characterizing ambient noise in lowlevel environments such as the National Parks. It presents definitions of terminology useful for understa...
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This document describes an ambient noise measurement protocol, a detailed methodology for characterizing ambient noise in lowlevel environments such as the National Parks. It presents definitions of terminology useful for understanding the measurement and assessment guidelines. Also included are a general overview, an historical perspective, and a statement of purpose and objective. Specific details of characterizing a study areas ambient noise are outlined, including measurement site selection, instrumentation, and general field measurement procedures. Particular attention is given to the data reduction and analysis methodology, including guidance on assigning actual measured ambient noise to all specific locations within a study area. Proposed field testing of the methodology and subsequent refinement are also discussed. Additionally, specifics on a low-level noise measurement system developed by the Volpe Center Acoustics Facility are included.
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Blade wake interaction noise (BWI) has been defined as the broadband noisegenerated by the ingestion of turbulent trailing tip vortices by helicopter rotors. This has been shown to be the dominant contributor to the subjectively i...
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Blade wake interaction noise (BWI) has been defined as the broadband noisegenerated by the ingestion of turbulent trailing tip vortices by helicopter rotors. This has been shown to be the dominant contributor to the subjectively important part of the acoustic spectrum for the approach stage of a helicopter flyover. A prediction method for BWI noise based on the calculated trailing vortex trajectories has been developed and estimates of the vortex turbulence have been made. These measurements were made on a trailing vortex from a split wing arrangement and did not give the spectrum of the velocity fluctuations. A recent experiment carried out to measure the turbulence associated with a trailing vortex and the application of the results to BWI noise prediction is described.
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