A low-frequency directional transducer with asymmetric shell

A low frequency directional transducer with compact structure is proposed. It is composed of a concave-convex asymmetric shell and a KNN-based lead-free piezoelectric ceramic driving element with lighter weight and smaller size. Both the large output of dipole mode and the small output of monopole mode could be excited simultaneously. And a series of advantages such as high acoustic power, low frequency directivity within small size could be achieved successfully by flexible design of concave-convex shell structural characteristics. It is shown that fine cardioid radiation pattern with a front to back pressure ratio of more than 20dB at about 1400Hz could be realized by finite element optimization analysis for single transducer element. Then another transducer with an extended structure of a double concave-convex shell is studied further. The results show that it has a lower frequency of 850Hz.