An acoustic transducer system for long-distance ranging applications in air

Abstract

Transducers for long-distance pulse-echo rangmg apphcauons should combme bgh efficacy and directwity with a relatively wide bandwdth Smce the air has a very low acoustic impedance, the effinent transnusslon of sound from a sohd transducer 1s one of the major problems A means to improve the impedance matchmg between the source and the propagation medium 1s to increase the radiation impedance by using extensive vibrating plates as radiators Nevertheless, these extensive radiators will vibrate at a flexural mode resonance, producing a poor directivity due to phase cancellation In this paper we present a transducer system, based on a stepped-plate rachator, which 1s able to generate eiliaently lngh-drrectional radiation m air To be used for pulse-echo rangmg apphcatlons, the stepped-plate rachator has been specially adapted m order to mcrease the bandwdth of the transducer system In particular, three mam features have been introduced the development of very thm stepped plates, the ad&ion of a matching layer, and the backing of the plate urlth a damping matenal Electroacoustical and pulse-echo characterlzatlons of the transducer system have shown its good performance for use as a level or distance sensor, specially for long-range apphcatlons (10-100 m)