Design of a low-frequency third-order super-cardioid directional source

In order to enhance the directivity gain of the primary pole in a circular array, a third-order super-cardioid sound source based on a uniform six-element circular array is proposed. The beam pattern of the sound source is investigated and analyzed by using the point source method, and an optimal scheme of the sound source is obtained. The single-sided radiation (SSR) flextensional transducer (FT) is selected as the sound source element to minimize the mutual radiation effect of the close-packed array. The acoustic radiation characteristics of the third-order super-cardioid source are studied by the finite element method. The findings demonstrate an 8 dB gain compared to the monopole sound source. A prototype is fabricated and tested. The test results confirm that the directional source exhibits a resonant frequency of 0.92 kHz with a transmitting voltage response of 139.0 dB. The −3 dB beamwidth is 56°, accompanied by all the sidelobes smaller than −15.0 dB. The feasibility of the optimized scheme is verified through the finite element calculations and measured results.