A Methodology for the Robust Estimation of the Radiation Pattern of Acoustic Sources

We propose a novel methodology for estimating the radiation pattern of acoustic sources, which is general enough as to be suitable for a wide variety of sources without the need of anechoic conditions of operation. Multiple plenacoustic cameras (which can be thought of as arrays of acoustic cameras) scan the source while keeping reflections and interferers at bay through deconvolution and windowing of the measured response. In the case of a moving source (e.g. a musical instrument while it is being played), the plenacoustic cameras are also used for tracking the position of the source. As for its orientation, we propose practical solutions for tracking that as well, whenever such information is not known in advance. Two experiments are conducted in order to validate the proposed solution. The former focuses on a commercial loudspeaker cabinet, whose radiation pattern is known in advance and can be used as groundtruth. The latter concerns violins, which exhibit an extremely rich and hard to predict acoustic behavior, due to their inherent structural and constructional complexity. Our method allows us to capture the radiation pattern of the instrument while it is being played, thus returning data corresponding to the natural timbre of the instrument, including the unavoidable acoustic shadow of the violinist's head. Experimental results confirm a relevant improvement in accuracy and robustness afforded by the adoption of dynamic plenacoustic solutions with respect to state-of-the-art techniques.

I. Introduction

The radiation or directivity pattern of an acoustic source is a frequency-dependent function that describes how it irradiates energy in space. The radiation pattern is very informative for an acoustician, as it reveals the directional properties of the source under analysis. Knowing the radiation pattern, particularly that of a musical instrument, is very important, as it allows us to understand how the source interacts with the surrounding environment, and how the audience perceives it.