This paper presents an approach with which perceived audible differences in aircraft sounds can be quantified and presented in an objective manner. The objective quantification of the subjectively heard audible differences is intended to serve two primary goals. It can firstly enable developers of auralization technology to make the auralized sounds more realistic by identifying in which aspects the synthesized sounds differ from their real-life counterparts and to what extent. The quantification can secondly provide an improved and more detailed means of distinguishing between aircraft sounds in general, beyond the conventional metrics of A-weighted Sound Pressure level (dBA) or Effective Perceived Noise Level (EPNL) used currently to assess aircraft noise. In this study sound quality metrics are used to quantify the differences in aircraft sounds. These metrics are widely used in other industries such as the automotive sector. Audio files of a reference aircraft, made over identical flight paths at a noise monitoring station in the vicinity of Schiphol airport, are compared in terms of both conventional and sound quality metrics for four measured and four auralized audio files. It is observed from the comparison that differences that may appear small in the conventional metrics can be significant in terms of the sound quality metrics. Significant differences in measured and synthesized sounds are observed for the aircraft considered in this study with regards to the tonal content and fluctuations in amplitude that occur over time. The conventional metrics are seen to capture the overall loudness aspect of aircraft sounds, but give no clear information regarding which spectral or temporal characteristics cause the sounds to be perceived as audibly different.@en

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This paper presents a methodology with which aircraft designs can be modified such that they produce optimal sound signatures on the ground. With optimal sound it is implied in this case sounds that are perceived as less annoying by residents living near airport vicinities. A novel design and assessment chain has been developed which combines the aircraft design process with an auralization and sound quality assessment capability. It is demonstrated how different commercial aircraft can be designed, their sounds auralized at representative locations in airport vicinities and subsequently assessed for sound quality. As sound quality is closely related to the perceived annoyance, it is expected that designs with improved sound quality would also be perceived as less annoying. By providing a feedback to the design optimizer in terms of one of the sound quality metrics or a suitable combination thereof, the designs of aircraft can be altered to produce potentially less annoying sounds. The paper will focus on three current aircraft and will demonstrate the application of the novel design chain to auralize and alter their sounds toward improved sound quality. The presented methodology can also be extended to unconventional aircraft configurations and propulsion concepts, for optimizing future aircraft sounds.@en

This paper presents an analysis of how flying Continuous Descent Approaches (CDAs) can affect the quality of sounds that aircraft produce in airport vicinities. It is well known that CDAs present potential benefits in terms of community noise impact with reductions in excess of 5 dBA in peak noise levels. It is however unclear if these reductions in A-weighted level, which is a poor predictor of perceived annoyance, also correspond to an improvement in the quality of the aircraft sounds that reach the residents on the ground. A real comparison can only be made by comparing the sounds an aircraft produces while flying a CDA with a standard approach procedure. A short-range and a long-range aircraft are simulated to fly a standard approach procedure and a CDA with 3, 4, and 5 degree glideslope angle. The noise produced over both approach procedures is then auralized at representative ground locations, and the sounds are analyzed for changes in sound quality. Quantifying the changes in the aircraft sounds in terms of sound quality metrics provides much clearer information regarding how the sound the residents hear has changed, and if the CDAs actually result in an improved sound quality and hence lower annoyance.@en

This paper presents an analysis of how flying Continuous Descent Approaches (CDAs) can affect the quality of sounds that aircraft produce in airport vicinities. It is well known that CDAs present potential benefits in terms of community noise impact with reductions in excess of 5 dBA in peak noise levels. It is however unclear if these reductions in A-weighted level, which is a poor predictor of perceived annoyance, also correspond to an improvement in the quality of the aircraft sounds that reach the residents on the ground. A real comparison can only be made by comparing the sounds an aircraft produces while flying a CDA with a standard approach procedure. A short-range and a long-range aircraft are simulated to fly a standard approach procedure and a CDA with 3, 4, and 5 degree glideslope angle. The noise produced over both approach procedures is then auralized at representative ground locations, and the sounds are analyzed for changes in sound quality. Quantifying the changes in the aircraft sounds in terms of sound quality metrics provides much clearer information regarding how the sound the residents hear has changed, and if the CDAs actually result in an improved sound quality and hence lower annoyance.@en

This paper presents a methodology with which aircraft designs can be modified such that they produce optimal sound signatures on the ground. With optimal sound it is implied in this case sounds that are perceived as less annoying by residents living near airport vicinities. A novel design and assessment chain has been developed which combines the aircraft design process with an auralization and sound quality assessment capability. It is demonstrated how different commercial aircraft can be designed, their sounds auralized at representative locations in airport vicinities and subsequently assessed for sound quality. As sound quality is closely related to the perceived annoyance, it is expected that designs with improved sound quality would also be perceived as less annoying. By providing a feedback to the design optimizer in terms of one of the sound quality metrics or a suitable combination thereof, the designs of aircraft can be altered to produce potentially less annoying sounds. The paper will focus on three current aircraft and will demonstrate the application of the novel design chain to auralize and alter their sounds toward improved sound quality. The presented methodology can also be extended to unconventional aircraft configurations and propulsion concepts, for optimizing future aircraft sounds.@en

This paper aims to present a way with which audible differences in measured and auralized (i.e. aurally simulated) aircraft noise can be quantified. The purpose of the study is to find a means with which the subjective differences between measured and synthesized sounds can be expressed in an objective manner. The quantification would firstly enable developers of auralization technology to identify more concretely in which aspects the differences exist, in order to make the auralizations sound more realistic. The quantification would secondly aid in developing a means of distinguishing between aircraft sounds in general, beyond the conventional metrics of A-weighted level (dBA) or Effective Perceived Noise Level (EPNL). Such a capability can allow target functions to be developed with which aircraft can be optimized for specific, more acceptable sounds. As used widely in other industries such as the automotive sector, use of sound quality metrics is made to quantify the differences in the quality of the sounds. The comparison is carried out in terms of both conventional and sound quality metrics for the audio of a reference aircraft, which has been measured and auralized over the same flight paths at a noise monitoring station in the airport vicinity. @en