Multi-horn matching plate for ultrasonic transducers

The problem of matching a thick piezoelectric transducer to an air medium is considered and it is concluded that a suitable matching device can be designed and built in the form of a rigid plate, a few millimetres thick and pierced by a closely packed array of horn-shaped channels, the wide mouths of the horns facing the external world and the narrow throats facing the transducer. Design parameters, particularly the spacing between the multi-horn plate and the transducer surface, are found to be quite critical, but well within ordinary manufacturing capabilities. Methods of fabricating the multi-horn plates are described and measured results presented. The measured performance agrees quite well with design calculations. The experimental plates show a gain of ~ 10 dB over a frequency range from ~30 to 100 kHz. Similar matching plates for other frequency ranges can be made.