Accession Number : ADA536390

Title :   Advanced Acoustic Model Technical Reference and User Manual

Corporate Author : WYLE LABS EL SEGUNDO CA

Personal Author(s) : Page, Juliet A ; Wilmer, Clif ; Schultz, Troy ; Plotkin, Kenneth J ; Czech, Joseph

Full Text :

Report Date : Sep 2010

Pagination or Media Count : 215

Abstract : 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 (NMSim) and the Rotorcraft Noise Model (RNM), that computes time varying noise levels for a user-defined flight trajectory. Developed under Strategic Environmental Research and Development Program project WP-1304 to address nonlinear sound propagation and complex directivity patterns from modern high thrust combat aircraft, it 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. Modeling includes the effect of thrust vectoring, implicit for rotorcraft and present on certain fixed wing aircraft. 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 Gee et al. Nonlinear propagation can affect spectra, noise metrics and the perceived quality of high amplitude jet noise. When invoked, the effects of sound propagation over varying ground terrain employs the geometrical theory of diffraction algorithms developed by Rasmussen. The effects of propagation through wind and temperature gradients over uniform terrain uses theory developed by Plotkin and Huber.


Subject Categories : Military Aircraft Operations
      Computer Programming and Software
      Solid Wastes Pollution and Control
      Terminal Flight Facilities

Distribution Statement : APPROVED FOR PUBLIC RELEASE