Portable goniometers with high angular resolutions and large radii for experimental investigations of acoustic diffractions

Surface scattering and diffuse reflections of acoustic diffusers are of relevance in room-acoustics simulations or for characterization purposes. Polar responses of diffraction objects to acoustic plane-wave excitations can be experimentally characterized using a circular microphone array: acoustical goniometer. Recently, the Graduate Program in Architectural Acoustics at Rensselaer Polytechnic Institute has begun to explore the advanced physical theory of diffraction (PTD) [Xiang and Rozynova, J. Acoust. Soc. Am., 141, pp. 3785 (2017)]. In order to validate the PTD applied to a number of canonical shapes (rigid wedges or plates) of finite sizes, experimental investigations on the diffraction objects need to be carried out with high angular resolutions and sufficiently wide angular ranges. A large radius of the acoustical goniometer is also crucial to satisfy acoustical far-field conditions. This talk will discuss the effort in implementation and processing algorithms for various radii of portable acoustical goniometers between 1 m and 4 m with angular resolutions up to 1.25 degrees, that can be easily deployed in indoor empty spaces of sufficient dimensions for an angular range across 180 degrees and beyond when diffusers or diffraction objects with one-axis symmetry need to be experimentally characterized.