ULTRASONIC ELECTRO-ACOUSTIC TRANSDUCERS

摘要

An ultrasonic electro-acoustic transducer (50) comprises a ceramic piezo-electric element (53) having a working face, bearing a first electrode structure (70), and a second face spaced from the said working face and bearing a second electrode structure (71). The transducer (50) is suitable for use in a short-range detection system having a transmission mode in which electrical driving signals are applied between the said first and second electrode structures (70, 71) to cause the element to vibrate so that ultrasonic acoustic waves are propagated, into a gaseous medium coupled to the said working face, towards a target position at a predetermined distance from the said working face, and having a reception mode in which such acoustic waves scattered back from an object at the said target position can cause the said element to vibrate so as to produce electrical signals indicative of the presence of such an object. The said working face is covered by a thin layer (54) of a silicone rubber, for enhancing transfer of acoustic energy between the said working face and the said gaseous medium, and other surface areas of the said element (53) are closely coupled to a solid damping body (52) of synthetic resin for dissipating energy in the said element between termination of the said transmission mode and commencement of the said reception mode.