An introduction to time-delay estimation, localization, and tracking in Acoustics

Abstract

Acoustic source localization and tracking has a long, productive history in both passive and active sonar signal processing. More recently, microphone arrays have been used to localize and track air acoustic noise sources. An overview of basic localization and tracking techniques of acoustic radiating sources and scatters is presented. For a wide range of applications, many ad-hoc passive and active source localization techniques have been investigated. Concepts from the statistical estimation theory, such as maximum likelihood estimators and Cramér-Rao lower bounds (CRLB), are useful benchmarks for evaluation of these practical ad hoc systems. In both air and underwater media, bearing and range estimates are determined by time-delay estimates; hence, properties of the time-delay estimates are of critical importance. In the case the of narrow-band active sonar, localization and tracking is based on time delay, Doppler, and direction of arrival estimation. In the case of wideband sonar and tracking of high-speed air acoustic sources, tracking and range estimates are determined from time-scale dilation estimates. CRLBs for active sonar are determined by signal-to-noise ratio, signal properties of signal ambiguity functions such as effective duration and mean-square bandwidth of the transmitted signal, and array parameters. [This work has been supported by ONR.]