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Full-Text Articles in Physical Sciences and Mathematics
Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein
Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein
Theses and Dissertations
Military aircraft generate high-amplitude noise which can cause injury to attending personnel. Efforts to mitigate the effects of this noise require a detailed understanding of the propagation of the noise, which was shown previously to be nonlinear. This thesis presents an analysis of high-amplitude noise propagation, emphasizing measures used to quantify the importance of considering nonlinearity. Two measures of the importance of nonlinearity are compared. These measures are the wave steepening factor and a skewness estimate. The wave steepening factor is a measure of how much nonlinear waveform steepening has occurred in a waveform. The skewness estimate is the skewness …
The Characterization Of Military Aircraft Jet Noise Using Near-Field Acoustical Holography Methods, Alan Thomas Wall
The Characterization Of Military Aircraft Jet Noise Using Near-Field Acoustical Holography Methods, Alan Thomas Wall
Theses and Dissertations
The noise emissions of jets from full-scale engines installed on military aircraft pose a significant hearing loss risk to military personnel. Noise reduction technologies and the development of operational procedures that minimize noise exposure to personnel are enhanced by the accurate characterization of noise sources within a jet. Hence, more than six decades of research have gone into jet noise measurement and prediction. In the past decade, the noise-source visualization tool near-field acoustical holography (NAH) has been applied to jets. NAH fits a weighted set of expansion wave functions, typically planar, cylindrical, or spherical, to measured sound pressures in the …