ABSTRACT
This chapter introduces and explains methods that can be used to locate and estimate the strength of acoustic sources. There are many approaches that can be taken to this problem, but the work presented here will principally address the techniques that make use of arrays of acoustic sensors and the methods used to process the signals output from the sensors. By far the most developed literature on this subject is that concerned with the location of underwater acoustic sources, where the sensors used are hydrophones and the signal processing methods are those associated with SONAR (SOund Navigation And Ranging). Here, however, whilst many of the basic results from this field will be referred to, the main emphasis will be on the use of microphone arrays for the location of sources of airborne sound. The chapter begins with an introduction to beamforming methods and
delineates the basic parameters that determine the ability of arrays to unambiguously resolve the angular location of far field sources. Simple methods for processing the signals from such arrays are also introduced and the influence of extraneous noise is dealt with. Least squares procedures are introduced together with matrix processing techniques when the problem posed is one of source strength estimation. Inverse methods are also dealt with in some detail and an attempt is made to clarify their relationship to Near-field Acoustic Holography (NAH). A description is also given of techniques used for the estimation of acoustic source strength distributions from far field measurements and a discussion is presented of the resolution limits of such procedures.
