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HQ PACAF proposes to establish new and increased combined exercises and interoperability at Royal Australian Air Force (RAAF) Bases Darwin and Tindal, located in the Northern Territory of Australia. This ER provides environmental analysis and documentation for these activities outside of the United States. The ER was prepared in accordance with Executive Order 12114, Environmental Effects Abroad of Major federal Actions Department of Defense Directive (DoDD) 6050.7, Environmental Effects Abroad of Major Department of Defense Actions, Title 32 of the Code of Federal Regulations (CFR) Parts 187 and 989, and applicable international agreements between the U.S. government and the government of Australia. This ER includes a statement of actions to be taken; identification of the important environmental issues involved; aspects of the actions taken or to be taken by the USAF that minimize the impact on the environment; and actions known to have been taken or planned to be taken by the government of any participating and affected foreign nations that may affect environmental considerations.

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., The original document contains color images.

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)1,2,3 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.

NMAP 7.0 is the most current version of the Department of Defense (DOD) computer program suite for the modeling of aircraft noise from aircraft flight and static events at an airbase. This report describes the features of the NOISEMAP (NMAP) 7.0 computer program and its operation. The entire suite encompassed by NMAP 7.0 includes several different programs. The three primary IBM-compatible PC-based programs in the suite are BASEOPS 7.0, NMAP 7.0, and NMPLOT 4.2. The report shows the relationship of these primary programs to the other secondary programs, as well as the conceptual flow of data. BASEOPS is used to enter all aircraft operational data including number of flight and static events, flight and static profiles, flight tracks, etc. NMAP is the computational module. This module accepts the data entered in the BASEOPS program, and estimates noise levels caused by aircraft events at many points on the ground in the airbase vicinity. NMPLOT is used to draw lines of equal noise level (noise contours) to determine the overall noise exposure and related environmental impacts (from aircraft and other sources).