Design of the Next Generation Aircraft Noise Prediction Program: ANOPP2

Abstract

The requirements, constraints, and design of NASA's next generation Aircraft NOise Prediction Program (ANOPP2) are introduced. Similar to its predecessor (ANOPP), ANOPP2 provides the U.S. Government with an independent aircraft system noise prediction capability that can be used as a stand-alone program or within larger trade studies that include performance, emissions, and fuel burn. The ANOPP2 framework is designed to facilitate the combination of acoustic approaches of varying fidelity for the analysis of noise from conventional and unconventional aircraft. ANOPP2 integrates noise prediction and propagation methods, including those found in ANOPP, into a unified system that is compatible for use within general aircraft analysis software. The design of the system is described in terms of its functionality and capability to perform predictions accounting for distributed sources, installation effects, and propagation through a non-uniform atmosphere including refraction and the influence of terrain. The philosophy of mixed fidelity noise prediction through the use of nested Ffowcs Williams and Hawkings surfaces is presented and specific issues associated with its implementation are identified. Demonstrations for a conventional twin-aisle and an unconventional hybrid wing body aircraft configuration are presented to show the feasibility and capabilities of the system. Isolated model-scale jet noise predictions are also presented using high-fidelity and reduced order models, further demonstrating ANOPP2's ability to provide predictions for model-scale test configurations.

Auralization of Hybrid Wing–Body Aircraft Flyover Noise from System Noise Predictions

“…Pseudo-recordings were post-processed using the ANOPP2 28 Acoustic Analysis API with a block size of 32,768 and a segment length of 0.5 s. Tone corrections located in bands below the 800 Hz 1/3-octave band were omitted from the PNLT and EPNL calculations to minimize the influence of non-aircraft sources such as ground reflections. Finally, it was found that for long propagation distances, the pseudo-recording in the 10 kHz 1/3-octave band was effectively numerically zero.…”

“…28 As part of that activity, the compatibility of ground impedance models employed in the auralization and system noise prediction needs to be assessed since only a hard ground plane was considered in this work. The straight-line propagation used in the existing auralization framework needs to be changed to allow specification of an average speed of sound along the slant range for compatibility with the system noise prediction.…”

“…Pseudo-recordings of the propagated synthesized noise are post-processed using the ANOPP2 28 Acoustic Analysis API to generate PNLT and EPNL for comparison with ANOPP generated metrics. Because engineering units are maintained through the simulation process, the two sets of metrics will be shown to compare favorably.…”

On Physical Aeroacoustics with Some Implications for Low-Noise Aircraft Design and Airport Operations

“…The incorporation of recent research can improve [358][359][360][361][362][363][364][365] relative to these widely used but simplified models by: (i) distinguishing different aircraft noise sources, both tonal and broadband, such as fan, turbine, jet and buzz-saw noise; (ii) allowing for atmospheric propagation and ground reflection and absorption effects (Section 3.1); (iii) including the effects of noise abatement procedures (Section 4.3) such as engine throttling; (iv) optimization of the sequences of take-offs and landings of different aircraft from multiple runways. In the present review the expression "airport noise" is taken in the broadest sense of all factors affecting the noise of aircraft near airports including: (i) aircraft noise sources (Section 2); (ii) atmospheric and ground effects and psychoacoustics (Section 3); (iii) noise reduction in the aircraft and noise abatement flight procedures (Section 4); (iv) low-noise aircraft design (Section 5).…”

A framework for simulation of aircraft flyover noise through a non-standard atmosphere

“…1,2 Because annoyance to both current and future aircraft may not be well captured by integrated noise metrics, there is a need for subjective assessments of individual flyovers. While many empirical and physics based methods are available to compute component and system noise, [3][4][5][6] their output is generally geared at producing frequency domain predictions or noise contours which are not well suited for subjective evaluation. Therefore, prediction-based noise synthesis is required to evaluate new designs (inclusive of changes to both source and operations) based on subjective measures.…”