Acoustic field generated by an innovative airborne power ultrasonic system with reflectors for coherent radiation.

In order to obtain the maximum efficiency in industrial processes assisted by airborne power ultrasound, the ultrasonic systems must be capable of generating an acoustic field with a maximum energy concentration in the desired areas. In this paper, the acoustic performance of two different ultrasonic systems is presented. The first system corresponds to an airborne power ultrasonic transducer with a flat rectangular plate radiator, and the second system is composed by the same transducer mounted in a set of reflectors that allow the generation of coherent radiation. The acoustic pressure field for each system has been determined numerically and the spatial pattern has been experimentally measured. In the experiment, the system with reflectors obtained higher pressure amplitude in a wider area, due to the coherent radiation achieved. The directivity pattern obtained in the experiment confirms this coherent radiation field. This is the first time that the acoustical behavior of two different ultrasonic systems with flat rectangular radiator, vibrating in a complex flexural mode, has been numerically and experimentally described and compared in terms of pressure amplitude distribution and directivity pattern.