NON-GAUSSIAN ACOUSTIC PRESSURE AMPLITUDES IN HIGH-INTENSITY SOUND FIELDS Revision C By Tom Irvine Email: tom@vibrationdata.com November 1, 2014 ____________________________________________________________________________ This is a work in progress. The following discussion refers to sound propagating through air. The sound pressure levels are referenced to 20 micro Pascals. Figure 1. XCOR Aerospace, Liquid Oxygen/Methane Rocket Engine, Test Firing Shock cells form in the plume core. Introduction The purpose of this paper is to consider acoustic waveforms where the time history and its corresponding histogram, or equivalent probability density function, are skewed, and thus Such cases are sometimes referred to as “one-sided.” Consider a supersonic rocket exhaust plume. The sound sources are Turbulent eddies form along the interface between the plume and the surrounding ambient air. The eddies themselves propagate at a supersonic velocity which is very roughly 80% of the jet exhaust velocity. The eddies generate shock waves as shown in Appendix A. Turbulent mixing the wake of the potential core, as shown in Appendix B. Supersonic exhaust jets are imperfectly expanded, or They contain “choked.” shock cells through which the flow repeatedly expands and contracts. The cells from a pattern inside the jet which appears as a series of diamonds, as shown in Figure 1 and in Appendix B.
NON-GAUSSIAN ACOUSTIC PRESSURE AMPLITUDES IN HIGH-INTENSITY SOUND FIELDS Revision C By Tom Irvine Email: tom@vibrationdata.com November 1, 2014 ____________________________________________________________________________ This is a work in progress. The following discussion refers to sound propagating through air. The sound pressure levels are referenced to 20 micro Pascals. Figure 1. XCOR Aerospace, Liquid Oxygen/Methane Rocket Engine, Test Firing Shock cells form in the plume core. Introduction The purpose of this paper is to consider acoustic waveforms where the time history and its corresponding histogram, or equivalent probability density function, are skewed, and thus Such cases are sometimes referred to as “one-sided.” Consider a supersonic rocket exhaust plume. The sound sources are Turbulent eddies form along the interface between the plume and the surrounding ambient air. The eddies themselves propagate at a supersonic velocity which is very roughly 80% of the jet exhaust velocity. The eddies generate shock waves as shown in Appendix A. Turbulent mixing the wake of the potential core, as shown in Appendix B. Supersonic exhaust jets are imperfectly expanded, or “choked.” They contain shock cells through which the flow repeatedly expands and contracts. The cells from a pattern inside the jet which appears as a series of diamonds, as shown in Figure 1 and in Appendix B.
nongaussian_acoustics_revC.docx