Studies of the Characteristics of a Densely-Coupled Array of Underwater Acoustic Transmitting Transducers

Abstract

The characteristics of a densely‐coupled array of underwater acoustic transmitting transducers are studied. At first, the electro‐acoustic characteristics such as the admittance, the resonant frequency and the transmitting voltage response, of a low frequency barrel‐stave flextensional transducer and a densely‐coupled compact array composed of three identical transducers uniformly distributed on a circle with spacing much less than half wavelength, are measured by experiments. Then, the radiation impedances of a single transducer and of transducers in the compact array are calculated by the boundary element model together with the finite element model. Based on the above results, the transducer’s equivalent circuit model parameters are calculated in different cases, which include a single transducer in air and in water, and a densely‐coupled array of three transducers parallel connected in water. The characteristics of the transducers and array are analyzed by the equivalent circuit model that was obtained. The research results show that when the transducers make up a densely‐coupled compact array, the resonant frequency decreases and the transmitting bandwidth broadens. It is also shown that the mutual interactions among elements are significant for the compact array. The mutual radiation resistance between two transducers is close to the self‐radiation resistance of the transducers. The vibration velocities of the transducers in the compact array are nearly 1/3 as those of a single transducer, and the radiation acoustic power and transmitting voltage response of the array are nearly the same as those of a single transducer, when the driving voltages of the array and single transducer are unchanged. Furthermore, the transmitting source level of the 3‐element compact array is 8.9dB higher than that of the single transducer if the vibration velocities of the transducers in the array are the same as those of the single transducer. The proposed technique can be used to design densely‐coupled compact arrays of transmitting transducers.