Noise pollution from air traffic is a major environmental problem, affecting airport communities. Aircraft flyover noise represents a complex auditory scenario wherein many acoustic and psycho-acoustic parameters other than loudness affect the annoyance perception. In order to investigate this, a new sound synthesizer tool was recently developed in the framework of the EU FP7 project "COSMA" (Community Oriented Solutions to Minimize aircraft noise Annoyance), allowing on-line and interactive sound quality analyses and target sound design of aircraft flyovers. Faders are assigned to the various tonal components (turbine, fan, airframe and buzz-saw tones) and broadband noise components (jet, fan, combustor and airframe noise), constituting an aircraft sound. These allow subjects to change the composition of the sound and compose a more preferred target sound with improved sound quality. The sound synthesizer includes mathematical rules for controlling fader interactions so that whenever one sound component is adjusted downwards by the listener, the others are controlled upwards, in order to compensate for total loudness. The tool only supports source component modifications, which are assumed to be technically realizable regarding engineering constraints within the coming 10-20 years. The fader input sound components have been generated for several types of airplanes that were measured in take-off and approach conditions. A dedicated sound decomposition algorithm was applied to extract the tonal components and broadband noise from the sound recordings. Source directivity and flight path information were used to further split the broadband noise into a jet, fan, combustor and airframe noise component. The output sounds of the sound synthesizer tool are very realistic and cannot be distinguished from the original recordings, when the faders are in the default position. In the coming years, the tool will play a key role in the "COSMA" project, in which many subjects from various countries will contribute to the sound synthesizer tests.
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