Janus-Helmholtz换能器的弱辐射耦合机理与带宽特性

针对Janus-Helmholtz (JH)换能器频带内响应起伏较大、模态耦合机制尚不明确的问题,提出了振动模态声辐射独立建模方法。该方法建立换能器各个振动模的独立有限元模型,在仿真计算中将位移载荷直接加载在辐射面上,分析振动模的辐射声场。通过各个结果的对比分析,观察到JH换能器声辐射模态的弱耦合规律,最终给出JH换能器带宽特性的合理物理解释,即JH换能器在同一纵向振子激励下,由于不存在声输出明显干涉加强的模态耦合,因此难以得到通常意义上响应起伏小于3 dB的宽带工作性能。以控制工作频带内响应起伏较小为前提,将拓宽工作频带作为设计目标,优化设计了 JH换能器结构参数。实验中换能器样机的发射电压响应测试结果与仿真计算相吻合,实测谐振频率为1350 Hz与2450 Hz,谐振频率下发射电压响应分别为143 dB,141 dB,在频带1200~3300 Hz范围内响应起伏12 dB,最大声源级204 dB,实现了宽带大功率发射的特性。

The weakradiation coupling and bandwidth characteristics of Janus-Helmholtz transducer

To solve the problems of the traditional Janus-Helmholtz(JH) transducer involving the indeterminacy of large response fluctuation and multiple-mode-coupling principle,the acoustic radiation performance of main independent vibration modes for the JH transducer are modeled separately and analyzed in detail by using the finite element method.It was found that weak radiation coupling occur between acoustic radiation models of JH transducer.The physical interpretation about the bandwidth characteristics could be given as follows by the results.Because no effective interference and enhancement could be used between the modes of a JH transducer with the same longitudinal driver,it would be quite difficult to obtain the broadband performance as usual.The optimization study of the electroacoustic performance is done to make its working bandwidth as broad as possible and the structural parameters is determined.At last a prototype is manufactured and measured.It is verified that the projector has good pe rformance by both the simulated and e xperimental re sults.The difference of TVR is about 12 dB in the frequency range from 1200 Hz to3300 Hz and the maximum source level is 204 dB.