Research shows that the sight of trees and the sound of moving water improve the soundscape quality of outdoor spaces exposed to road traffic noise. Effects are attributed to non-energetic masking, visual attentional distortion and congruence between sight and hearing. However, there is no literature on such effects for aircraft noise. Aircraft noise varies from other traffic sources, i.e. in terms temporal variability, duration and spectral composition, complicating the application of findings without further research. In a VR experiment reported in this article, participants were asked to rate scenarios with different sound levels of flyovers, urban typologies, vegetation and/ or water features. The results showed a significant improvement of the soundscape quality when 1) vegetation and 2) moving water were present, and especially when 3) vegetation and moving water were presented simultaneously, especially for residential areas in terms of the relative change. Moving water also reduced the saliency of aircraft flyovers significantly, changing the constellation of fore-and background sounds. Moving water raised the perceived audibility of the most dominant sound source too, which could be attributed to non-energetic masking effects. Our findings indicate that soundscape strategies can complement noise abatement in areas prone to aircraft noise.

Aircraft noise is consistently rated as more annoying than noise from other sources with similar intensity. In three experiments, it was investigated whether this penalty is due to the source identity of the noise. In the first experiment, four samples were played to participants engaged in a working memory task: road traffic noise, an Airbus 320 flyover, and unidentifiable, transformed versions of these samples containing the same spectral content and envelope. Original, identifiable samples were rated as more annoying than the transformed samples. A second experiment tested whether these results were due to the absence of tonal components in the transformed samples. This was partly the case: an additional sample, created from the A320 flyover by filtering out major tonal components, was rated as less annoying than the original A320 sample, but as more annoying than the transformed sample. In a third experiment, participants either received full disclosure of the generation of the samples or no information to identify the transformed samples. The transformed sample was rated as most annoying when the A320 identity was disclosed, but as least annoying when it was not. Therefore, it was concluded that annoyance is influenced by both identifiability and the presence of tonal components.

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226SECKEL, ELLIS, AND OLCOTT J. AIRCRAFT same time. This is the case with the decelerating technique at VDEC approach speed. 5) With the decelerating technique, the penalties in difficulty of control and landing distance caused by either excess speed or steep angles are very slight. In the experiment, typical landing distances varied from a little over 600 ft at 7 = 3° to a little under 1000 ft at 7 = 18°. 6) In VFR conditions, as the approach path angle is steepened, the difficulty of the landing gradually increases. Larger rates of descent, higher flare point and increased flare normal acceleration are the contributing factors. Under IFR conditions, these factors would probably severely limit the minimum ceilings that would be operational.NASA, working with American Airlines, has completed the first phase of research to evaluate the operational feasibility of two-segment approaches for noise abatement. For these tests, area navigation was used to establish the upper glide slope and an ILS was used to establish the lower. The flight director was modified to provide command information during the entire approach. Twenty-eight pilots representing the airlines, professional pilot associations, FAA, and NASA participated. With an ILS approach for comparison, the procedure gave a noise reduction of 18 EPNdb at the outer marker and 8 EPNdb 1.1 naut miles from touchdown.

AhstrnctFlyover measurements of the.airframe noise of AeroCommander , JetStar, CV-990, and R-747 aircraft are presented. Data a r e shown for both cruise and landing configurations. Correlations between airframe noise and aircraft parameters a r c developed and presented, The landing approach nirframe noise for the test aircraft was approximatcly 10 EPNdB below present FAA certification requirements.