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Aircraft noise

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


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DOI
10 Nov 2018
TL;DR: In this article, the authors present a detailed literature review on the most common aerospace noise sources, challenges in aero-acoustic measurements, and the acoustic imaging methods typically used to overcome them.
Abstract: With the continuous growth in demand for air traffic and wind turbines, the noise emissions they generate are becoming an increasingly important issue. To reduce their noise levels, it is essential to obtain accurate information about all the sound sources present. Phased microphone arrays and acoustic imaging methods allow for the estimation of the location and strength of sound sources. Experiments with these devices are one of the main approaches in the current research in aeroacoustics, along with computational simulations or noise prediction models. This thesis presents a detailed literature review on the most common aerospace noise sources, challenges in aeroacoustic measurements, and the acoustic imaging methods typically used to overcome them. Practical recommendations are provided for selecting the appropriate imaging technique depending on the type of experiment. New integration techniques for distributed sound sources, such as leading– or trailing–edge noise, are proposed in this thesis and are proven to provide the best performance in retrieving the source levels, compared to other well–known methods. In addition, the high–resolution version of the deconvolution method CLEAN–SC, HR–CLEAN–SC, is explained and applied to wind–tunnel measurements. It is confirmed that this method can resolve sound sources at half the frequency associated with the Rayleigh resolution limit, while keeping the inherent advantages of CLEAN–SC. The most appropriate acoustic imaging methods (according to the recommendations from the literature study) were applied to aeroacoustic experiments and compared with other approaches, when possible. Since the landing gear is considered as the dominant airframe noise source in commercial aircraft, this source was analyzed using four different approaches: aircraft flyover measurements under operational conditions, full–scale wind–tunnel experiments, computational simulations and noise prediction models. Strong tonal noise at certain frequencies was observed and suggested the presence of open cavities. Noise prediction models do not account for this behavior and seem to provide erroneous estimates. Eliminating the contribution of the cavity will reduce the noise levels considerably. Trailing–edge noise is considered to be the dominant noise source for modern wind turbines. The performance of the two most promising noise reduction measures was investigated in wind–tunnel experiments. First, trailing–edge serrations featuring different geometries were studied and showed noise reductions of more than 10 dB. In case a serration–flow misalignment angle occurs, the performance of the serrations decreases and they even cause a noise increase after a crossover frequency. Similar results were found with computational simulations. Secondly, trailing–edge porous inserts showed noise reductions of approximately 10 dB at low frequencies and a noise increase after a crossover frequency. It is argued that the reasons for these phenomena were, respectively, the cross–flow between the pressure and suction sides of the airfoil and the increased roughness of the porous material with respect to the solid case. Lastly, the issue of the variability in aircraft noise levels was considered, since it is not properly taken into account by current best practice noise prediction models and hinders the enforcement of environmental laws. It was observed that variations in the fan rotational speed explain a large part of this variability. Two different approaches were proposed for estimating the fan rotational speed of aircraft flyovers based on audio recordings. Implementing these more accurate estimates of this parameter in the noise prediction model (rather than the default values as usual) considerably reduces the errors made and provide more accurate aircraft noise estimates. In conclusion, phased microphone arrays have confirmed their importance for aeroacoustic studies, such as measuring aircraft noise emissions under operational conditions and assessing the performance of noise reduction measures.

21 citations

01 Nov 1972
TL;DR: A theoretical model for the generation of blade-passage noise caused by the interaction of rotor wakes with the downstream stator blades in a fan stage has been compiled and a set of significant parameters has been identified to reduce this interaction-caused blade-Passage frequency noise.
Abstract: A theoretical model for the generation of blade-passage noise caused by the interaction of rotor wakes with the downstream stator blades in a fan stage has been compiled. This model has combined a description of the rotor wake based on existing experimental correlations with an existing theory for the response of the stator blades to those wakes. This model of the interaction-caused blade-passage noise has been used to examine some effects of blade geometry and flow conditions on the noise generated. A set of significant parameters has been identified to reduce this interaction-caused blade-passage frequency noise. A redesign of an existing fan with the use of these concepts has produced a theoretical noise reduction of more than 7 decibels.

21 citations

Proceedings ArticleDOI
05 Jan 2015
TL;DR: In this article, a slat-gap filler (SGF) is used to close the gap between the slat and the main wing of an aircraft to reduce airframe noise.
Abstract: Noise produced by unsteady flow around aircraft structures, termed airframe noise, is an important source of aircraft noise during the approach and landing phases of flight. Conventional leading-edge-slat devices for high lift on typical transport aircraft are a prominent source of airframe noise. Many concepts for slat noise reduction have been investigated. Slat-cove fillers have emerged as an attractive solution, but they maintain the gap flow, leaving some noise production mechanisms unabated, and thus represent a nonoptimal solution. Drooped-leading-edge (DLE) concepts have been proposed as "optimal" because the gap flow is eliminated. The deployed leading edge device is not distinct and separate from the main wing in DLE concepts and the high-lift performance suffers at high angles of attack (alpha) as a consequence. Elusive high-alpha performance and excessive weight penalty have stymied DLE development. The fact that high-lift performance of DLE systems is only affected at high alpha suggests another concept that simultaneously achieves the high-lift of the baseline airfoil and the noise reduction of DLE concepts. The concept involves utilizing a conventional leading-edge slat device and a deformable structure that is deployed from the leading edge of the main wing and closes the gap between the slat and main wing, termed a slat-gap filler (SGF). The deployable structure consists of a portion of the skin of the main wing and it is driven in conjunction with the slat during deployment and retraction. Benchtop models have been developed to assess the feasibility and to study important parameters. Computational models have assisted in the bench-top model design and provided valuable insight in the parameter space as well as the feasibility.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the challenges and quantified goals as developed by the Advisory Council for Aeronautics Research in its Strategic Research Agenda would influence and contribute to the improvement of the next generation of civil transport aircraft.

21 citations

Journal ArticleDOI
TL;DR: Results confirm the importance of both acoustical parameters for the prediction of short-term annoyance due to nocturnal aircraft noise and importance of the frequency of fly-overs for the Prediction of annoyance reactions.
Abstract: The German Aerospace Center (DLR) investigated in the NORAH sleep study the association between a distinct change in nocturnal aircraft noise exposure due to the introduction of a night curfew (11:00 p.m.–5:00 a.m.) at Frankfurt Airport and short-term annoyance reactions of residents in the surrounding community. Exposure–response curves were calculated by random effects logistic regression to evaluate the aircraft noise-related parameters (1) number of overflights and (2) energy equivalent noise level LASeq for the prediction of short-term annoyance. Data of the NORAH sleep study were compared with the STRAIN sleep study which was conducted by DLR near Cologne–Bonn Airport in 2001/2002 (N = 64), representing a steady-state/low-rate change. The NORAH sleep study was based on questionnaire surveys with 187 residents living in the vicinity of Frankfurt Airport. Noise-induced short-term annoyance and related non-acoustical variables were assessed. Nocturnal aircraft noise exposure was measured inside the residents’ home. A statistically significant rise in the portion of annoyed residents with increasing number of overflights was found. Similarly, the portion of annoyed subjects increased with rising LASeq. Importance of the frequency of fly-overs for the prediction of annoyance reactions was emphasized. The annoyance probability was significantly higher in the NORAH than in the STRAIN sleep study. Results confirm the importance of both acoustical parameters for the prediction of short-term annoyance due to nocturnal aircraft noise. Quantitative annoyance models that were derived at steady-state/low-rate change airports cannot be directly applied to airports that underwent a distinct change in operational and noise exposure patterns.

21 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202386
2022103
202152
202051
201980
201878