Frederik Rietdijk

​Auralisation of airplanes considering sound propagation in a turbulent atmosphere

Aircraft noise is a major issue in urban areas. Due to a rising level of urbanisation and the continuing growth of air traffic more people are exposed to aircraft noise than ever. Methods currently used for assessing the
impact of aircraft noise on humans consider mostly energetic quantities, and not the dynamic character of the sound. Therefore, in order to obtain a more accurate picture of the impact of aircraft sound it may be helpful to assess how the audible sound is perceived.

Auralisation is a method for rendering audible sound fields and may be used to create audible aircraft sound. A tool was developed to auralise the sound of jetairplanes and consists of an outdoor sound propagation model and an emission synthesiser. The emission synthesiser computes an emission signal consisting of tonal
components and broadband noise. The spectral components vary over time and take into account directivity.
An inverse propagation model was developed to compute back from a receiver to source in time-domain. An automated procedure was developed to extract features from the resulting signal. These features were then used to directly synthesise the emission as function of time, and this signal was propagated to the original
receiver resulting in an auralisation that should reproduce the recording it is based on.

To validate the auralisation tool, a listening test was conducted where participants were presented with recordings and auralisations and had to rate their similarity. Results indicate that differences exist between the auralisations and recordings. Improving the synthesis of the blade passing frequency is expected to improve the similarity between auralisations and recordings.

Finally, fluctuations can typically be noticed when listening to sound from a distant aircraft, and one cause of these fluctuations is atmospheric turbulence. A computationally fast algorithm was developed to take into account the amplitude and phase modulations that arise as the sound propagates through the turbulent atmosphere. According to the author the method results in improved plausibility of the auralisations.

Keywords: Atmospheric turbulence,Aircraft noise, Auralisation, Outdoor sound propagation
Fakultetsopponent: Dr. Stephen Rizzi, NASA Langley Research Center, Hampton VA, USA
Examinator och huvudhandledare: Professor Wolfgang Kropp, Avdelningen för teknisk akustik, ACE, Chalmers
Biträdande handledare: Professor Jens Forssén, Avdelningen för teknisk akustik, ACE, Chalmers
Kategori Disputation
Plats: SB-L516, Sven Hultins gata 6
Tid: 2017-09-22 10:00
Sluttid: 2017-09-22 12:00

Publicerad: ti 04 jul 2017. Ändrad: to 31 aug 2017