A novel airborne longitudinal-flexural ultrasonic radiator with ABH-curved beam

Longitudinal-flexural ultrasonic radiators offer advantages including high radiation efficiency, high power handling capacity, and controllable radiation directivity. This paper presents an ultrasonic radiator integrating a Langevin transducer with an ABH-curved metallic beam. The acoustic black hole (ABH) structure modulates and amplifies the displacement amplitude on the radiating surface, significantly improving the airborne acoustic radiation capability of the ultrasonic radiator. Under resonance system design, the resonance frequency of the ABH-curved beam is analytically determined using the transfer matrix method combined with Timoshenko beam theory. Numerical simulations are conducted to investigate the relationship of the radiator's radiation characteristics on the ABH geometric exponent. Two experimental prototypes of the ABH and ordinary types are fabricated, and their equivalent electrical impedance, vibration characteristics, and acoustic pressure distribution are systematically measured. Excellent agreement between measured and simulated results validates the effectiveness of the ABH structure in simultaneously improving both structural vibration capability and acoustic radiation performance.