Acoustic particle motion measurement for bioacousticians: principles and pitfalls

Abstract

It is currently thought that all fishes detect acoustic particle motion, and it is therefore critical to measure this vector quantity when studying hearing, acoustic behavior, and noise impacts. Proper measurement of particle motion in any of its forms (acceleration, velocity, or displacement) is subject to a range of errors whose magnitude depends on the sound source(s) of interest and the environments in which they are observed. Particle motion measurement principles and errors have primarily been addressed in the literature for free field plane waves. However, such fields are rarely encountered in bioacoustic studies, and experiments or calculations made based on plane wave assumptions can lead to substantially erroneous measurement results and flawed study conclusions. This paper presents a unified treatment of underwater acoustic particle motion measurement by reviewing acoustic field attributes of commonly encountered source/environment scenarios, quantifying measurement error sources, and concludin...