Aircraft noise

About: Aircraft noise is a research topic. Over the lifetime, 3051 publications have been published within this topic receiving 32039 citations.

The Joint Rolls-Royce/Boeing Quiet Technology Demonstrator Programme

Abstract: *† ‡ § ** †† This paper describes a successful programme undertaken by Boeing and Rolls-Royce to demonstrate nacelle based noise reduction technologies including advanced nozzle and enhanced inlet nacelle designs. The programme, completed between 2001 and 2002, demonstrated jet noise reductions in flight, of up to 4dB, for hot and cold nozzle serrations, confirming pre-test expectations based on model test work. Forward propagating fan noise reductions of up to 13dB were achieved at blade passing frequency (BPF) with a new Boeing developed acoustically enhanced inlet (Amax). Acoustic pressure transducer arrays located forward and downstream of the fan, during static engine testing, helped identify that the Amax inlet fan noise reductions were largely attributable to minimising scattering of acoustic modes and the axial extent of the new liner. Results from this programme highlight the benefit of engine and airframe manufacturers working together to reduce overall aircraft noise levels, and have demonstrated the readiness of the tested technologies for production incorporation.

Full-Scale Turbofan-Engine Turbine-Transfer Function Determination Using Three Internal Sensors

Abstract: Existing NASA/Honeywell EVNERT full-scale static engine test data is analyzed by using source-separation techniques in order to determine the turbine transfer of the currently sub-dominant combustor noise. The results are used to assess the combustor-noise prediction capability of the Aircraft Noise Prediction Program (ANOPP). Time-series data from three sensors internal to the Honeywell TECH977 research engine is used in the analysis. The true combustor-noise turbine-transfer function is educed by utilizing a new three-signal approach. The resulting narrowband gain factors are compared with the corresponding constant values obtained from two empirical acoustic-turbine-loss formulas. It is found that a simplified Pratt & Whitney formula agrees better with the experimental results for frequencies of practical importance. The 130 deg downstream-direction far-field 1/3-octave sound-pressure levels (SPL) results of Hultgren & Miles are reexamined using a post-correction of their ANOPP predictions for both the total noise signature and the combustion-noise component. It is found that replacing the standard ANOPP turbine-attenuation function for combustion noise with the simplified Pratt & Whitney formula clearly improves the predictions. It is recommended that the GECOR combustion-noise module in ANOPP be updated to allow for a user-selectable switch between the current transmission-loss model and the simplified Pratt & Whitney formula. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The Subsonic Fixed Wing Project's Reduce-Perceived-Noise Technical Challenge aims to develop concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. The reduction of aircraft noise is critical to enabling the anticipated large increase in future air traffic.

A Quest for Quiet Commercial Passenger Transport Aircraft for Take-off and Landing

Abstract: Noise pollution in communities living close to airports world-wide could have been avoided if, following the Second World War, Governments and Local Planners had built the very large commercial airports according to strong directives and regulations preventing the building of houses in zones closer than 2 − 3km from the airport boundary fence. Today the problem of noise nuisance in communities living close to airports is world-wide. The noise nuisance during the approach to landing is set by CTOL aircraft following the 3deg. ILS glide slope. All commercial aircraft thus fly at high lift, referred to as the ‘dirty configuration’, from a height of about 300m. altitude to touchdown, a distance of about 6km., including the dropping of the undercarriage while the aircraft is flying low over residential areas. The noise on the ground far exceeds the noise of a ‘clean aircraft’ if such an aircraft could fly at the same approach speeds. This paper reviews possible future aircraft technology that could avoid aircraft flying low over residential areas and so permit the introduction of a mandatory height exclusion zone of at least 1000m. above all residential areas. It is found that the use of STOL aircraft incorporating circulation control, and preferably integrated lift and propulsion systems could be designed to meet this objective and would allow the undercarriage to be lowered during a continuous descent much closer to the airport boundary fence. Further research is required to ensure such aircraft make no increase in noise over current CTOL aircraft operating at the same distance. Since the STOL aircraft will be flying higher and slower, and its take-off and landing distance will be shorter, the noise reduction from this greater separation in distance from residential ares would result in noise reductions in these communities of at least 20dB, a target which has become the International goal for aircraft noise reduction in current research programs.

Toward noise certification during design: airframe noise simulations for full-scale, complete aircraft

Abstract: An overview of a recent, NASA-sponsored effort to substantially advance simulation-based airframe noise prediction is presented. An accurate characterization of this component of aircraft noise requires a high-fidelity representation of the finer geometrical details associated with the landing gear and wing high-lift devices, such as slats and flaps, which constitute major noise sources. To achieve this ambitious goal, a systematic approach was followed to extend our current state-of-the-art computational tools to a full-scale, complete aircraft in landing configuration within a realistic flight environment. The work involved several phases: high-fidelity, large-scale, unsteady flow simulations; model-scale experiments in ground-based facilities; and farfield noise prediction for a full-scale, complete aircraft. The comprehensive aeroacoustic database generated during the course of the 6-year effort provided a wealth of relevant information for full validation and benchmarking of the advanced computational tools used in the present work. The database will also foster the development of simulation methodologies with improved predictive capabilities.

Effects of aircraft noise on an intelligibility task.

Abstract: The recorded sounds of three aircraft (T28 propeller airplane, Bell 204B helicopter, and Bell 206 helicopter) flying directly overhead at 300 ft and 900 ft (91.4 m and 274.3 m) were played While subjects engaged in an audiovisual task. The subjects viewed a series of 35-mm color slides of everyday scenes and heard them described by one-word labels. Each label was to be identified as "Right," "Wrong," or "Unheard." The results were in close agreement with previous field studies on the rated "annoyingness" of aircraft sounds and provided no support for the contention that impulsive helicopter noise ("blade-slap") is disruptive in ways not accoullfed for by simple measures of loudness level