Design and Fabrication of a Wideband Cymbal Transducer for Underwater Sensor Networks

Cymbal transducers are characterized by a high mechanical quality factor and low power efficiency. The research conducted so far on cymbal transducers has focused on improving the power efficiency and structural stability, but modern underwater sensor network systems need transducers to have a wide frequency bandwidth as well. In this study, a wideband cymbal transducer was designed to fill that need. First, the effect of various structural parameters on the performance of the cymbal transducer was analyzed with emphasis on the bandwidth using the finite element method. Based on the analysis results, the structure of the cymbal transducer was optimized to have the widest possible bandwidth while maintaining its transmitting voltage response (TVR) level over a typical power requirement as well. The validity of the design was verified by fabricating a prototype of the optimized cymbal transducer and comparing its measured performance with the design

Selection of a Potting Material and Method for Broadband Underwater Cymbal Arrays

Cymbal transducers are often used in arrays for underwater communication and detection systems. The working environment of a cymbal array is underwater; therefore, waterproofing, salt-corrosion prevention, and impact resistance are necessary for stable operation of the array. Hence, we simulated potting a cymbal array with 15 different rubber and epoxy materials available in the market, using the finite element method, and analyzed their effect on the transmitting voltage response spectrum of the array. From the analysis results, we selected the material that would achieve the widest frequency bandwidth, while preserving the structural stability of the array. A potting method corresponding to the selected material was suggested as well. This study provides guidelines for the selection of a potting material for use in underwater transducer arrays

Design of an Acoustic Bender Transducer for Active Sonobuoys

Recent underwater vehicles can operate with a much lower level of noise, which increases the need for an active sonobuoy with a high detection performance. These active sonobuoys mainly use bender transducers as a projector that emits sound waves. In this study, we designed a high-performance bender transducer and verified the validity of the design through experiments. For this purpose, first we analyzed the variation of the peak transmitting voltage response (TVR) level and peak TVR frequency of the bender transducer, in relation to its structural parameters. The performance of the bender transducer was analyzed using the finite element method. Then we derived the optimal structure of the bender transducer to achieve the highest TVR. Based on the design, a prototype of the bender transducer was fabricated and its acoustic properties were measured to confirm the validity of the design

Design of a Piezoelectric Multilayered Structure for Ultrasound Sensors Using the Equivalent Circuit Method

This study investigates the electroacoustic behavior of a piezoelectric multilayered structure for ultrasonic sensors using the equivalent circuit method (ECM). We first derived the vertical deflection of the multilayered structure as a function of pressure and voltage using equilibrium equations of the structure. The deflection derived in this work is novel in that it includes the effect of piezoelectricity as well as the external pressure on the radiating surface. Subsequently, the circuit parameters were derived from the vertical deflection. The acoustic characteristics of the structure were then analyzed using the electro-acoustical model of an ultrasonic sensor for in-air application. Using the equivalent circuit, we analyzed the effects of various structural parameters on the acoustic properties of the structure such as resonance frequency, radiated sound pressure, and beam pattern. The validity of the ECM was verified initially by comparing the results with those from the finite element analysis (FEA) of the same structure. Furthermore, experimental testing of an actual ultrasonic sensor was carried out to verify the efficacy of the ECM. The ECM presented in this study can estimate the performance characteristics of a piezoelectric multilayered structure with high rapidity and efficiency

Equivalent Circuit to Analyze the Transmitting Characteristics of a Cymbal Array

A cymbal transducer has a simple structure consisting of a piezoceramic disk and metallic caps and has broadband characteristics when built as an array. The finite element method (FEM) is generally used to analyze the characteristics of acoustic transducers. However, the FEM requires a longer analysis time as the model becomes larger, which makes it limited and less efficient for analyzing the cymbal array. In this study, a new equivalent circuit with higher efficiency and accuracy, comparable to that of the FEM, was proposed to analyze the performance of cymbal arrays. The equivalent circuit for the array was constructed by connecting the equivalent circuits of individual cymbal transducers in parallel with a radiation impedance matrix that included both the self- and mutual radiation characteristics of the array. The validity of the new equivalent circuit was verified by measuring the transmitting voltage response of a cymbal array specimen and comparing it with that calculated using the circuit. The comparison confirmed the efficiency of the equivalent circuit in analyzing the characteristics of the cymbal array. The proposed equivalent circuit can facilitate the design of a large array of cymbal transducers

Development of a Dual-Layer Structure for Cymbal Transducer Arrays to Achieve a Wider Bandwidth

Cymbal transducers are typically grouped and arranged in planar arrays. For projector arrays, a wide bandwidth on the transmitting voltage response (TVR) spectrum is required for better underwater communication and data transmission within a short time. The purpose of this study is to develop a wideband cymbal array by controlling the center-to-center (CTC) spacing between the cymbal transducers in the array. In the practical design of the array, due to the arrangement of elements in one layer, the minimum CTC spacing between the cymbals is constrained to the diameter of the cymbals in use. To overcome this limitation, we propose a new dual-layer array structure. Finite element analysis of the cymbal array showed that the bandwidth was generally inversely proportional to the CTC spacing. We explained the mechanism of this relationship using a theoretical analysis of the mutual radiation impedance between the cymbals in the array. Subsequently, we identified the optimum CTC spacing to achieve the widest possible bandwidth for the cymbal array. The validity of the wideband array design was verified through the fabrication and characterization of prototype arrays. We confirmed that the two-layered arrangement could significantly widen the bandwidth of the cymbal array while maintaining the TVR above a specified level