Broadband Janus-Helmholtz transducer with various liquid cavity resonances

Abstract

To enhance the radiation capacity of the Janus-Helmholtz transducer (JHT) and achieve a broadband transmitting response, an asymmetric dual-cavity JHT is proposed and a broadband symmetric multi-cavity JHT design is introduced. Firstly, the vibration characteristics of the cylindrical liquid cavity are analyzed and two liquid cavities with different dimensions are utilized to construct the asymmetric dual-cavity JHT. The operating principles of both the typical JHT and the asymmetric dual-cavity JHT are revealed. Furthermore, an equivalent circuit model (ECM) for the asymmetric dual-cavity JHT is proposed by combining the ECMs of the Janus transducer and the liquid cavities. To validate the accuracy and generality of the ECM for the asymmetric dual-cavity JHT, four JHTs are fabricated and tested, and the finite element method (FEM) is also employed to predict their electroacoustic performance. The admittance obtained from ECM, FEM and experiment (EXPT) exhibit good agreement. Additionally, the radial transmitting voltage response (rTVR) calculated by FEM aligns well with the experimental results. Experimental results demonstrate that the asymmetric dual-cavity JHT, compared to its typical counterpart of the same dimensions, exhibits a significantly increased rTVR within the low-frequency band. Moreover, the directivity of the typical JHT and the asymmetric dual-cavity JHT are compared by FEM and the causes of radial response fluctuations in the asymmetric dual-cavity JHT are analyzed. Finally, a symmetric multi-cavity JHT with a lower resonant frequency and a wider operating bandwidth is designed through FEM, verifying the effectiveness of the multi-mode coupling design principle. The ECM for the dual-cavity JHT offers valuable theoretical support for optimizing JHT designs and the symmetric multi-cavity JHT design serves as inspirations for modifying resonant frequency, enhancing emission capability and advancing operating bandwidth of the JHTs.