An atmospheric turbulence model plugin for the NASA auralization framework

Abstract

Temporal and spatial fluctuations in wind and temperature affect sound propagation causing both amplitude and phase modulations, or scintillations. The amplitude modulations can be heard, e.g., when listening to a distant aircraft. The phase modulations cause additional decorrelation between different propagation paths. NASA has been developing a software framework for the purposes of auralizing sound. The framework allows users to synthesize aircraft noise at a moving source and propagate it to a listener. This propagation occurs in the time domain through the application of gain, time delay, and filters. The framework includes a plugin architecture for rapid integration of new modules. A model has been developed to simulate the scintillation effects of acoustic propagation through a turbulent atmosphere. Further, this model has been implemented as a plugin to the NASA auralization framework. The turbulence model plugin generates a time-varying filter along each propagation path that describes the frequency dependent amplitude and phase modulations. The framework converts the filter descriptions to finite impulse responses, which are appended to other propagation filters, including atmospheric absorption and ground impedance. Because real scintillations can be heard, inclusion of the model is demonstrated to result in higher fidelity auralizations than those generated without the model.