Accuracy of a passive acoustic location system: empirical studies in terrestrial habitats

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Abstract
The accuracy with which an acoustic location system (ALS) could locate a sound source was studied in open meadow and woodland habitats for a number of types of sound. The ALS used differences in the arrival times of sound at a fixed, four-microphone array and was based on the Canary sound analysis package. Location error increased with distance of the sound source from the centre of the array and was smallest in meadow habitats which induced little reverberation and which had low levels of biological background noise. The physical characteristics of sound elements could be used to predict the accuracy of the ALS in locating them. In general, frequency modulated sounds were located more accurately than constant frequency sounds, as were sounds containing a number of different elements when compared with shorter, single-element sounds. It proved to be possible to locate sounds routinely to within a few tens of centimetres, and therefore song perch changes of a few metres could be detected by the ALS. Thus this system has the potential to become an essential tool with which to study animals generating sounds, in particular acoustic signalling and communication networks.