All WP3 tasks have been completed according to plan.
Noise propagation models were developed in WP3, which include the effects of atmospheric temperature gradients and non-uniform wind on sound and effects of rough ground and atmospheric absorption on aircraft noise.
For the use of the noise prediction scheme of SOPRANO, numerical models were built for i) airframe, ii) engine and iii) full aircraft. The numerical results were compared with experimental data from literature for an assessment of SOPRANO. The airframe model results were found to reproduce the experimental data in almost all situations. The numerical engine models are of much lower quality due to missing parameters and data.
In order to overcome the disadvantage of monaural sound reproduction, which is a loss of authenticity which may influence the perception of annoyance significantly, a 3D sound reproduction method was developed to enhance the degree of authenticity.
The development of the Sound Synthesis Machine (SSM) was done in WP3, the examinations started in July 2011 after extensive pre-tests. The examinations clearly showed that the newly developed Sound Machine is a very suitable instrument to identify and alter sound components to achieve less annoying aircraft sounds which promises valid results for further problems in the future.
Beside the SSM, the ANCS (Airport Noise Climate Synthesizer) is an important tool of COSMA. The tool was finalized and the complete ANCS chain from source spectra to synthesized flyover noise was successfully validated in a joint WP3/5 activity to test and validate the ANCS chain including the modelling of the AC noise sources and their propagation to the ground, the synthesis of audio signals and their comparison to noise recordings. The exercise was done for an Airbus A320 in take-off and approach condition. Public domain source prediction models were developed for i) airframe noise, ii) fan-compressor noise and iii) jet noise. In order to find out whether the ANCS synthesized sounds correspond to natural aircraft sounds, a laboratory listening test was set up (22 subjects) for comparing both types of sound psychometrically relative to various perceptual attributes such as loudness, annoyance, tonality and pitch. This psychometric validation showed, that the ANCS synthetic sounds are very well able to simulate authentic aircraft flyover events. It was furthermore shown that the 3D method is capable to successfully simulate a spatial sound environment which is much more effective than one generated by stereo or mono sound reproduction.
The synthesis of different airport scenario sounds was one very important task in WP3. Those sounds are used in the WP2 laboratory tests to investigate the importance of i) aircraft sound quality and ii) flight path on the perception of annoyance.
The main objectives of WP3 are:
In order to achieve these objectives, the WP3 research activities are distributed over 3 tasks: