Aircraft noise

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

Combined Noise Exposure at Home

Abstract: In everyday life people are simultaneously exposed to several sound sources, which emerge from background soundscapes of considerable variability due to building layouts, residential pattern, topography, meteorology, and lifestyle. In contrast, noise regulation, planning, and control treat the sound environment by separating it into pieces and describe it by a one-number indicator. This practice ignores the possibility of any effect modification (by inhibition, partial or full additivity, or synergism). This effect modification can take place not only between sound sources (multisource issue) but also with simultaneously occurring environmental factors (vibration and air pollution) from the same source or through other contextual factors (multistressor issue). What people know about auditory perception of combined sound exposure mainly rests on experimental work using short-term loudness judgments in repeated designs in controlled settings. Recent psychoacoustic experiments did not find full support for the most prevalent models in practice (e.g., simple energy summation), when the context of the assessment is more carefully distinguished (sound heard within combined sound or alone). The findings are difficult to compare with field studies where long-term judgments of annoyance take place in the immediate context of the subject's living environment. The combined noise paradox is such a finding. It describes the phenomenon that total annoyance is often judged equal or even lower than the dominant source alone. Some call it compromise judgments suggesting them to result from ambiguous questions or misinterpretations of the frame of reference when total annoyance should be assessed. In experiments, compromise judgments were observed mainly with unequally loud and time-separated sounds. But also increases in total annoyance have been observed in the field studies. Although masking partly explains lower annoyance, higher annoyance due to equally loud sources is less well understood. Further effect modifications have been observed with simultaneously occurring vibrations, low-frequency annoyance, and tonal and impulsive components of heterogeneous sound sources such as those from industry. The larger annoyance effects observed can vary in terms of decibel equivalents between −3 and +15 dBA. The highest values are associated with impulsive noise and low background noise context. Eventually, air pollution and other contextual factors can further contribute to total annoyance. Incomplete accountance of effect modifications in environmental risk assessments will lead to errors in planning and less than optimal noise control.

Computer program to predict aircraft noise levels

Abstract: Methods developed at the NASA Lewis Research Center for predicting the noise contributions from various aircraft noise sources were programmed to predict aircraft noise levels either in flight or in ground tests. The noise sources include fan inlet and exhaust, jet, flap (for powered lift), core (combustor), turbine, and airframe. Noise propagation corrections are available for atmospheric attenuation, ground reflections, extra ground attenuation, and shielding. Outputs can include spectra, overall sound pressure level, perceived noise level, tone-weighted perceived noise level, and effective perceived noise level at locations specified by the user. Footprint contour coordinates and approximate footprint areas can also be calculated. Inputs and outputs can be in either System International or U.S. customary units. The subroutines for each noise source and propagation correction are described. A complete listing is given.

Strategic Noise Mapping of Herakleion: The Aircraft Noise Impact as a factor of the Int. Airport relocation

Abstract: Abstract In the framework of the European Directive 2002/49/EC, the city of Herakleion in Crete Island (Greece) recently completed (2013) its Strategic Noise Map (SNM) and relevant Noise Action Plan (NAP). Strategic noise mapping and action plans are important tools to define the main strategies to reduce noise exposure of residents and introduce and preserve \"quite zones\". Within this framework and as a part of the Herakleion city Strategic Noise Mapping general a specific analysis was introduced in the urban area of Alikarnassos (east part of the city) adjacent to the International Airport “Nikos Kazantzakis”. The 2nd biggest airport in Greece, airport is proposed to be relocated in Kastelli area (some 37 km south of the Herakleion city centre, far away from dense populated areas), within the next decade but in the mean time, air traffic (take of, taxi and landing procedures, especially during the extended spring and summer period), are affecting the city. This paper analyzes the extended acoustic measurement monitoring program and the modelling of environmental noise levels within the city’s SNM introducing - state of the art - qualitative surveys on the sound perception and noise annoyance by the residents as well as in depth analysis of the urban and architectural tissue. All these results have been transcribed in several maps introducing a very comprehensive evaluation tool towards an efficient noise action plan leading to the eventual relocation of the airport. This paper presents the main results of this research aiming to the evaluation of the inffluence at the inhabitants’ sonic comfort from aircraft operation.

Assessment of Current Jet Noise Prediction Capabilities

Abstract: An assessment was made of the capability of jet noise prediction codes over a broad range of jet flows, with the objective of quantifying current capabilities and identifying areas requiring future research investment. Three separate codes in NASA s possession, representative of two classes of jet noise prediction codes, were evaluated, one empirical and two statistical. The empirical code is the Stone Jet Noise Module (ST2JET) contained within the ANOPP aircraft noise prediction code. It is well documented, and represents the state of the art in semi-empirical acoustic prediction codes where virtual sources are attributed to various aspects of noise generation in each jet. These sources, in combination, predict the spectral directivity of a jet plume. A total of 258 jet noise cases were examined on the ST2JET code, each run requiring only fractions of a second to complete. Two statistical jet noise prediction codes were also evaluated, JeNo v1, and Jet3D. Fewer cases were run for the statistical prediction methods because they require substantially more resources, typically a Reynolds-Averaged Navier-Stokes solution of the jet, volume integration of the source statistical models over the entire plume, and a numerical solution of the governing propagation equation within the jet. In the evaluation process, substantial justification of experimental datasets used in the evaluations was made. In the end, none of the current codes can predict jet noise within experimental uncertainty. The empirical code came within 2dB on a 1/3 octave spectral basis for a wide range of flows. The statistical code Jet3D was within experimental uncertainty at broadside angles for hot supersonic jets, but errors in peak frequency and amplitude put it out of experimental uncertainty at cooler, lower speed conditions. Jet3D did not predict changes in directivity in the downstream angles. The statistical code JeNo,v1 was within experimental uncertainty predicting noise from cold subsonic jets at all angles, but did not predict changes with heating of the jet and did not account for directivity changes at supersonic conditions. Shortcomings addressed here give direction for future work relevant to the statistical-based prediction methods. A full report will be released as a chapter in a NASA publication assessing the state of the art in aircraft noise prediction.