Aircraft noise

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

Computational AeroAcoustics of a Realistic Co-Axial Engine, possibly equipped with Acoustic Liners

Abstract: The present work is devoted to the numerical simulation of acoustic emissions characterizing turbojet engines, a subject that is relevant of the more general purpose of aircraft noise prevision and reduction. More precis ely, we explore here the ability of a structured / time-domain CAA (Computational AeroAcoustics) method/solver to address complicated problems of engine noise prediction. With that end, and by using the ONERA’s CAA solver sAbrinA.v0 , we conduct realistic calculations of aft fan nois e emissions, such computations involving a full-3D exhaust geometry (with its pylon / internal bifurcations) to be possibly equipped with noise absorbing materials (acoustic liner). Being conducted for a representative fan noise modal content (high azimut hal order / frequency) and within realistic flight conditions (take-off), such calcul ations deliver insights of both phenomenological / physical and methodological / numerical natures; firstly, it is here shown how far aft fan noise emissions can be reduced by a proper use of absorbing materials. Secondly, it is further demonstrated how ‘industria l-like’ engine noise problems can be handled via numerical simulations based on a structured / time-domain CAA approach.

The Aircraft Noise Problem

Abstract: Aircraft noise presents a system problem which to date has been attacked mainly at the level of individual components. The system includes: (a) aircraft as noise sources; (b) atmosphere and terrain as influences on sound propagation; (c) people, under several classes and conditions, as responders to noise; (d) physical components for controlling noise; (e) operating procedures for reducing noise exposure in communities; (f) public relations; (g) aviation planning policies and economics; and (h) many organizations concerned with characteristics and consequences of aircraft noise. The nature of these components is reviewed in a general way, with emphasis on their inherent interrelations. This discussion provides a framework for unifying the several subjects included in the present Aircraft Noise Symposium.

A comparison between the impact of noise from aircraft, road traffic and trains on long-term recall and recognition of a text in children aged 12-14 years.

Abstract: A total of 417 students in the seventh grade, 12-14 old, took part in three 15 min learning sessions in their ordinary class-rooms. Their task was to read a text, and they were tested one week later with difficult recall questions and less difficult recognition items on the text. The first session was a pretest for their learning abilities. This session was run in ambient noise conditions and all the students read the very same text. The scores from this session were employed to split the pupils along the median into two groups of learning ability. Sessions two and three were counterbalanced as a noise condition or an ambient noise condition. In these sessions two other texts were employed, and they appeared equally often under the noise and ambient conditions, as well as under the two different presentation orders. Three subgroups of the pupils were exposed to aircraft noise, train noise and road-traffic noise. The noise types were of the same equivalent level (66 dB(A) Leq) in all subgroups. The design of the study permitted two different analyses of long-term learning. First, in a within subject analysis, the difference scores between the noise and ambient noise conditions in session 2 and 3 were calculated, and crossed with learning ability (high and low) and type of noise. In a second between subject analysis, the difference scores in session 1 and 2 were crossed with the group factor whether they had noise or ambient conditions in session 2, and the ability and noise type factors. Both analyses yielded the same results. Noise impaired long-term recall of the difficult items. Degree of impairment on the recall items did not interact with noise source or learning ability. The average impairment due to aircraft and road traffic noise was around 23% of the scores. Train noise had no effect. For the easy recognition items there were no effects of noise exposure, nor of its interaction with noise source and learning ability. Since the number of pages read did not differ between noise and ambient conditions, an explanation in terms of distraction is ruled out. The results are discussed in terms of arousal and cognitive overload.