Comparative Study of the Vibromechanical Characteristics of Compact Hydroacoustic Longitudinal-Bending Type Transducers with a Complex Radiating Shell Shape

Abstract

The development of compact hydroacoustic low-frequency emitters with a high power density is fraught with difficulties due to conflicting requirements on the dimensions, efficiency, radiated power, operating bandwidth, and manufacturability. For compact emitters, the body dimensions limit the possibility of combining the resonances of the active element and mechanical oscillatory system, which makes their development difficult. A compact hydroacoustic low-frequency longitudinal-bending type transducer with a complexly shaped radiating surface, 3D LFR, designed for large-scale modeling and verification of theoretical calculations of such design, has relatively small dimensions and demonstrates high efficiency. The paper presents the results, obtained with laser vibrometry, of in-air measurements of the vibrational characteristics of two titanium bodies with different sizes and corrugation patterns. The proposed designs for the transduce with maximum overall dimensions of less than 100 mm and a weight of approximately 1 kg provide a voltage sensitivity of about 1 Pa m/V in the operating frequency band and the fundamental resonance in the 1–2 kHz range. 3D LFR has a high mechanical conversion coefficient and uses the added mass; it also has a number of other advantages over similar designs. It is shown that the 10–12% differences in the sizes of the two emitters and the geometry of the radiating shells (12 and 16 corrugation waves) lead to a difference in the resonance frequencies measured in air (4.0 and 3.5 kHz, respectively). At the same time, the emitter is larger and has a smaller spread of the mechanical conversion coefficient along the ridges and troughs of the body, as well as a denser distribution of the spectral components outside the fundamental frequency band.