Acoustic Array Systems

1

Introduction

An acoustic array system refers to a collection of acoustic transducers operating concurrently for certain acoustic signal process purposes. Acoustic transducers operating in audible range and air medium are predominantly loudspeakers and microphones. In particular, microphone array technologies have received considerable research interest as a means of enhancing voice quality and, more recently, visualizing sound fields, and identifying noise sources. Despite the fact that the sensors being discussed in this book are microphones, the signal processing methodology is to a great extent influenced by the farfield array signal processing predecessors in radio waves. Not limited to the radio wave applications, array signal processing technologies [1–8] has found their way into many application areas nowadays, such as non-destructive evaluation [9, 10], underwater imaging [11, 12], machine diagnosis [13, 14], and so forth. For a number of reasons, arrays serve as an appealing solution for these application scenarios. First, by properly using the array, the signal-to-noise ratio (SNR) of noise-corrupted signals can usually be increased. Second, arrays per se are spatial filters, which enables manipulation of array directivity (also referred to as beamforming). This feature is appealing in that it allows us to focus on the primary source of interest while rejecting noise and reverberation in the background. Third, the beam can be “electronically steered” by incorporating ...