Abstract
Spatial and temporal inhomogeneities in temperature and wind velocity affect sound propagation resulting in amplitude and phase fluctuations called scintillations. A computationally efficient method is presented to generate sequences of scintillations. The method, already used in the field of wireless communication to predict the performance of wireless communication links, could be used in the field of acoustics to create more perceptually valid auralizations. A Gaussian spectrum and a spherical wavefront is considered, but the method can also be used in combination with other spectra like the Von Karman spectrum as well as plane waves. Two examples are given, one is a pure tone affected by the scintillations and the other is an auralization of an aircraft fly-over. The effect of the transverse speed of the source is demonstrated as well.
Highlights
In an outdoor situation, spatial and temporal variations in temperature and wind velocity cause small changes in the refractive index
In this paper we will continue to use the covariance for spherical waves and a Gaussian spectrum, because the Gaussian spectrum is the simplest model to work with and computationally least demanding, but the method can be used with covariance functions that describe other turbulence spectra, like e.g. the Von Karman spectrum [16]
The impulse response of the filter is obtained by taking the Inverse Discrete Fourier Transform (IDFT)
Summary
Spatial and temporal variations in temperature and wind velocity cause small changes in the refractive index. As waves pass through the atmosphere, the index-of-refraction variations in effect cause scintillations, i.e. fluctuations in the received intensity of the wave. Scintillations affect both sound and electromagnetic waves. Fluctuations due to turbulence have been included in auralizations by simulating the amplitude modulations that were observed in measurements [1, 7]. In this paper a method is presented to generate time series of sound pressure fluctuations caused by line-ofsight propagation through a weakly turbulent atmosphere. Novel in this field, the method includes both log-amplitude. The method was used by the authors to increase the perceptual validity of auralizations [10, 11]
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