Sealed, matched piezoelectric transducer

A sealed ultrasonic transducer assembly for use adjacent a fluid of characteristic acoustic impedance Z.sub.4, comprising,

• an electroacoustic transducer element having a front surface and a rear surface and a characteristic acoustic impedance Z.sub.1,
• an impedance-transforming matching element positioned in contact with the front surface of said transducer element,
• an electrically conductive shielding housing having an aperture for transmitting ultrasonic radiation from said transducer assembly, and
• a sealing element enclosing said aperture and hermetically sealed to said housing,
• said matching element being formed of a non-resilient material having an effective characteristic impedance intermediate between that of said transducer element and said fluid;
• said sealing element having an acoustic impedance higher than that of said matching element by a factor of at least 2 and having a thickness between 1/10th and 1/1000th of a wavelength at the center frequency of ultrasonic waves being transmitted from said transducer element, said sealing element being electrically conductive over at least one surface, said electrically conductive housing being in electrical contact with said electrically conductive surface;
• the combination of said sealing element, matching element and transducer being restrained axially and radially within said housing.