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Advanced Acoustic Model Technical Reference and User Manual

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The Advanced Acoustic Model AAM is a suite of computer programs that predicts far-field noise for single or multiple flight vehicle operations of fixed wing or rotary wing aircraft. It is a time simulation model, evolved from Noisemap Simulation Model NMSim1,2,3 and the Rotorcraft Noise Model RNM,4,5 that computes time varying noise levels for each step in a user-defined flight trajectory. It was developed under Strategic Environmental Research and Development Program project WP-1304, in response to a need to address nonlinear sound propagation and complex directivity patterns from modern high thrust combat aircraft. It fits within the current NOISEMAP6 system of aircraft noise modeling, and will eventually replace NOISEMAP as updated noise sources are developed. AAM includes all of the capabilities of RNM. AAM is based on three dimensional noise sources defined about a vehicle moving along a trajectory. Three dimensional source modeling includes the effect of thrust vectoring, implicit for rotorcraft and present on certain fixed wing aircraft. Propagation from the vehicle to receivers accounts for geometric spreading, air absorption and finite ground impedance. For high thrust military aircraft, nonlinear propagation effects associated with high noise levels are computed. It can optionally account for varying ground terrain or atmospheric gradient effects. Sources are generally defined as one-third octave band spectra. A Narrowband and pure tone modes are available, should there be a particular need. The Doppler shift associated with vehicle motion is included in the analysis, as is the propagation time from the source to the receiver. Nonlinear propagation effects are addressed using the theory developed by Gee7,8 et al. Nonlinear propagation can affect spectra, noise metrics and the perceived quality of high amplitude jet noise.

Subject Categories:

  • Computer Programming and Software
  • Acoustics
  • Noise Pollution and Control

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