Tonpilz type underwater vector sensor with directional sensitivity to acoustic waves.

Abstract

Typical Tonpilz-type underwater acoustic transducers making use of piezoceramics detect the magnitude of an acoustic pressure, a scalar quantity, and convert this pressure into a proportional output voltage. The scalar sensor has no directional sensitivity. In this paper, a new Tonpilz transducer structure is proposed to measure both the magnitude and the direction of an incoming acoustic wave with a single transducer unit, which is accordingly referred to as a vector sensor. The piezoceramic stack clamped between the head mass and the tail mass of a Tonpilz transducer is divided into four radial segments, each segment polarized alternately to its neighboring one. An acoustic pressure wave coming from outside causes positive or negative signed electric voltage signals in the piezoceramic segments in accordance with their polarization directions as well as a certain amount of time delay between the electric signals. Proper manipulation of the electric signals, i.e., pairing the segments and either adding or subtracting the signals of the paired segments, can provide the relationship between the signals and the magnitude and direction of the acoustic wave. Feasibility of this structure is confirmed through 3-D simulations of the receiving properties of the transducer with the finite element method.