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Typical underwater acoustic sensors can measure the magnitude of an incoming sound wave but cannot identify the direction. In this paper, a new simple method for detecting the direction of a sound wave with a piezoelectric ring hydrophone is proposed. This method divides the piezoceramic ring of the hydrophone into eight elements and distinguishes the direction of the sound wave by combining the output voltages of the elements in a particular manner. The validity of the design method was confirmed through the fabrication of an experimental prototype of the ring hydrophone with the proposed structure and a comparison of its performance with the design results. The method allows the ring vector hydrophone to operate over a very wide frequency range without being restricted to its structural resonant frequencies.

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Typical underwater Tonpilz transducers detect the magnitude of an acoustic pressure, a scalar quantity, by means of piezoceramic rings, and convert this pressure into a proportional electric voltage. The scalar sensor has no directional sensitivity. This paper proposes a new vector sensor based on the Tonpilz transducer that is sensitive to both the magnitude and direction of an incoming acoustic wave. The piezoceramic rings of the new Tonpilz-type vector sensor are divided into four quadrant segments. The direction of an incoming acoustic wave is identified by combining the output voltages of the four piezoceramic segments in a particular manner. The operation frequency range of the vector sensor follows that of conventional Tonpilz transducers. The feasibility of this new structural design has been confirmed through a three-dimensional simulation of the operation of the vector sensor with the finite element method. The validity of the new design is verified by fabricating and characterizing an experimental prototype of the vector sensor.

Tonpilz transducers are desirable for their superior performance in underwater target detection and communication applications. Several design schemes to widen their bandwidth have been reported, but these schemes often involve a complex structure or arrangement of additional components. In this study, a simple design is proposed to improve the bandwidth of a multimode Tonpilz transducer by using a non-uniform drive section that consists of piezoelectric stacks of various thicknesses. The efficacy of the design is illustrated with a multimode Tonpilz transducer having three lead zirconate titanate (PZT) stacks of different thicknesses. A new equivalent circuit was developed to analyze the frequency response of the transducer incorporating the non-uniform drive section and was used for rigorous analysis of the effects of varying the position and thickness of the non-uniform stacks on the transmitting characteristics of the transducer. The validity of the design was verified through the fabrication and characterization of a prototype multimode Tonpilz transducer. The developed structure can be readily extended to an arbitrary number of stacks in the Tonpilz transducer with any number of PZT disks in each stack.