Motion simulation in the environment for auditory research

Virtual sound source motion has been implemented in the Army Research Laboratory's Environment for Auditory Research, which contains a 57-channel spherical loudspeaker array located in an anechoic chamber. Using the Psychophysics Toolbox Version 3 low-latency PortAudio API, 57 channels of streaming audio are dynamically updated in real-time using MATLAB for signal processing. Both distance-based amplitude panning (DBAP) and vector base amplitude panning (VBAP) have been implemented in MATLAB for controlling source motion. Sources are defined on a given path, such as a circle, ellipse, or the “dog bonex”; flight pattern often used in aviation. While DBAP works convincingly for virtual sources located on the sphere defined by the loudspeaker array, VBAP is needed to position sources outside the array. Source motion paths are defined parametrically with respect to time, and playback buffers update the panned position every 11.6 ms. Based on the source's instantaneous distance, diffuse-field or free-field amplitude attenuation is added in MATLAB as well air absorption filtering. This system will be used for a variety of audio simulations and auditory experiments.