An ultrasonic transducer for vibration mode conversion of wedge-shaped structure of acoustic black hole

TL;DR

This paper introduces an ultrasonic transducer with an acoustic black hole wedge structure that enhances vibration mode conversion, enabling applications like ultrasonic levitation and particle manipulation through gradient sound pressure distribution.

Contribution

It presents a novel ultrasonic mode-conversion transducer incorporating an ABH wedge radiant plate, with theoretical modeling, simulation, and experimental validation demonstrating its effectiveness.

Findings

Vibration frequencies match between theoretical model and finite element simulation.

The transducer produces a gradient sound pressure distribution.

Experimental results confirm the transducer's feasibility for ultrasonic levitation.

Abstract

Acoustic black hole (ABH) structure has been extensively employed in applications such as vibration mitigation, noise reduction, and energy harvesting, owing to its unique sound wave trapping and energy concentration effects. Furthermore, ABH structure shows significant promise in improving the performance of ultrasonic device and constructing multifunctional acoustic field. Therefore, this paper proposes an ultrasonic mode-conversion transducer consisting of a Langevin transducer and an ABH wedge radiant plate to investigate the potential applications of ABH in ultrasonic levitation and multifunctional particle manipulation. The theoretical model of flexural vibration of the radiant plate was established by utilizing Timoshenko beam theory and transfer matrix method, and the calculated vibration frequencies demonstrated good agreement with those obtained from finite element simulations (FES). The electrical impedance frequency response characteristics, vibration modes and the near-field sound pressure distribution of the transducer in air were also simulated. The results revealed that the amplitude of the ABH wedge radiant plate increases stepwise, and the sound pressure exhibits a gradient distribution. A prototype of the transducer was fabricated and experimentally tested, confirming the accuracy of FES and the feasibility of the design approach. Finally, the ultrasonic levitation experiment demonstrated that the ABH design enables the formation of gradient distribution of sound pressure in the standing wave sound field, thereby facilitating precise particle sorting.