Identification of Nonlinear and Near-field Effects in Jet Noise Using Nonlinearity Indicators

In the collection and analysis of high-amplitude jet noise data for nonlinear acoustic propagation, both model-scale and full-scale measurements have limitations. Model-scale measurements performed in anechoic facilities are usually limited by transducer and data acquisition system bandwidths and maximum propagation distance. The accuracy of fullscale measurements performed outdoors is reduced by ground reflections and atmospheric effects. This paper describes the use of two nonlinearity indicators as complementary to ordinary spectral analysis of jet noise propagation data. The first indicator is based on an ensemble-averaged version of the generalized Burgers equation. The second indicator is the bicoherence, which is a normalized version of the bispectral density. These indicators are applied to Mach-0.85 and Mach-2.0 unheated jet noise data collected at the National Center for Physical Acoustics. Specifically, the indicators are used to separate geometric near-field effects from nonlinear propagation effects for the Mach-2.0 data, which cannot be done conclusively using comparisons of power spectral densities alone.

[1]  James Lighthill,et al.  The inaugural theodorsen lecture , 1994 .

[2]  J. Gallagher,et al.  Experiments on the nonlinear characteristics of noise propagation from low and moderate Reynolds number supersonic jets , 1981 .

[3]  Kent L. Gee,et al.  Investigation of a Single-Point Nonlinearity Indicator in the Propagation of High-Amplitude Jet Noise , 2006 .

[4]  Kent L. Gee,et al.  Nonlinear Propagation of Noise Radiated from Supersonic Jets , 2004 .

[5]  James Lighthill.  Some aspects of the aeroacoustics of high-speed jets , 1993 .

[6]  D. Crighton,et al.  Nonlinear propagation of broadband jet noise , 1980 .

[7]  Kent L. Gee,et al.  Measurement and Prediction of Noise Propagation from a High-Power Jet Aircraft , 2006 .

[8]  U. Greb,et al.  The interpretation of the bispectrum and bicoherence for non-linear interactions of continuous spectra , 1988 .

[9]  D. G. Crighton.  Nonlinear Acoustic Propagation of Broadband Noise , 1986 .

[10]  Steve Elgar,et al.  Statistics of bicoherence , 1988, IEEE Trans. Acoust. Speech Signal Process..

[11]  Dennis K. McLaughlin,et al.  Acoustic Pressure Waveforms Measured in High Speed Jet Noise Experiencing Nonlinear Propagation , 2005 .

[12]  James Bridges,et al.  Experimental and Analytical Determination of the Geometric Far Field for Round Jets , 2005 .

[13]  E. Powers,et al.  Digital Bispectral Analysis and Its Applications to Nonlinear Wave Interactions , 1979, IEEE Transactions on Plasma Science.

[14]  Kent L. Gee,et al.  Bispectral Analysis of High-Amplitude Jet Noise , 2005 .

[15]  Dennis K. McLaughlin,et al.  Experiments on the Non-linear Propagation of Noise from Supersonic Jets , 2003 .

[16]  G. P. Howell,et al.  Nonlinear Propagation of Aircraft Noise in the Atmosphere , 1980 .

[17]  Kent L. Gee,et al.  Preliminary Analysis of Nonlinearity in Military Jet Aircraft Noise Propagation , 2005 .

[18]  R. Haubrich.  Earth noise, 5 to 500 millicycles per second: 1. Spectral stationarity, normality, and nonlinearity , 1965 .

[19]  Semih M. Ölçmen,et al.  High-intensity rocket noise: nonlinear propagation, atmospheric absorption, and characterization. , 2005 .

[20]  M. Hinich.  Testing for Gaussianity and Linearity of a Stationary Time Series. , 1982 .

[21]  Krishna Viswanathan,et al.  Instrumentation Considerations for Accurate Jet Noise Measurements , 2006 .