The outer cavity Janus-Helmholtz with sound insulation layer is presented for ob- taining the capacity of high-power non-directional transmitting. The radiation efficiency and directivity in the 0 degrees direction can be improved when the radiation mode is changed by laying sound insulation layer. The operating bandwidth can be expanded effectively by the dual mode coupling between the cavity vibration and longitudinal vibration of Janus transducer. A prototype is designed by finite element method. Test results show that the results are in good agreement with the design results. Compared with inner cavity Janus-Helmholtz transducer, acoustic radiation performance of outer cavity Janus-Helmholtz underwater acoustic transducer in the 0 degrees direction has been significantly improved.
为了解决Janus-Helmholtz水声换能器研究中的理论问题,通过互辐射模型时的Janus-Helmholtz水声换能器等效电路,分析了Janus换能器纵振动谐振频率在水中升高的原因;通过对Janus换能器纵振动和液腔振动的相频曲线的分析,得出了Janus-Helmholtz水声换能器宽带发射的机理,研究了腔体弹性对Helmholtz声学性能的影响规律。设计了工作频段为1~3 k Hz的Janus-Helmholtz换能器试验样机,样机的测试结果表明其振动及声学特性与理论研究结果相符。
An underwater acoustic transducer with dual-Helmholtz resonators is presented.The acoustic output of flexural disc transducer below its resonant frequency can be amplified by Helmholtz resonators,the"∞"-shaped beam pattern can be obtained due to in-phase radiation of two Helmholtz resonators.Thus,the transducer has the characteristic of low frequency directional transmitting which is difficult for low frequency,small size transducers.The principle of achieving directivity for the low frequency transducer is described.The acoustic performance is studied by a finite element model.The influence of key structural parameters such as the length of cavity,the thickness of metal disc in flexural disc transducer and the thickness of simply supported structure on Helmholtz resonant frequency have been investigated.The transmitting voltage response and directivity are solved.The prototype is fabricated based on simulation result,and the transmitting voltage response and directivity are tested in anechoic tank.Test results revealed that the transducer has"∞"-shaped vertical directivity at Helmholtz resonant frequency,the beampattern and Helmholtz resonant frequency are in good agreement with simulation results.The transducer presented in this paper can provide technical support for low frequency directional transmitting with small size.
