A compact quartz oscillator includes a quartz vibrator that is integrally mounted on a circuit substrate. In the quartz oscillator, flux residue can be easily washed away. A cavity is defined in the approximate center of the circuit substrate. Within the cavity, circuit components defining an oscillation circuit, a temperature-compensating circuit, and other such circuits are surface-mounted preferably via reflow soldering. Connection electrodes are disposed at the four corners of walls surrounding the cavity. The connection electrodes are bonded to electrodes of the quartz vibrator mounted on the circuit substrate preferably via reflow soldering. Recesses are provided in the top surfaces of the walls. With the recesses, clearances are created between the circuit substrate and the quartz vibrator. As a result, in order to wash away flux residue.

The present invention provides an acoustic sensor having one or more segments that are electrically coupled to provide a response corresponding to a hydrodynamic pressure applied to the segments. Each segment contains a substrate of a desired shape with a concavity on an outer surface that is sealingly enclosed by an active member made from a flexible, resilient piezoelectric material. PVDF material is preferably used as the piezoelectric active element. The active member is covered with a protective layer of a suitable material, preferably a polyvinyl material. A single segment may be used as a sensor or a plurality of suitably configured segments may be suitably coupled to form the sensor. The sensor may be used as a hydrophone on a hydrophone cable commonly used for performing seismic surveys for geophysical exploration. In such applications, a plurality of hydrophones are placed equally spaced along the cable. In the preferred embodiment, two hydrophone segments are securely be placed around the cable. The segments are electrically coupled to each other and to a conductor in the cable. In operation, the hydrophone cable is placed at the bottom of a water-covered area or towed behind a seismic vessel to conduct seismic surveys.

A plurality of grooves are radially formed in an annular frame and an annular plate is secured to the frame to form a sound discharge hole in each groove, thereby communicating a back chamber under a diaphragm with the atmosphere. A projected part is outwardly projected from a peripheral edge of the annular plate, and an adhesive is adhered to a peripheral edge of a protector and to an upper surface of the projected part to adhere the protector with the annular plate.

A piezoelectric acoustic component having excellent efficiencies of productivity and of acoustic conversion, a greatly miniaturized size, and excellent impact resistance properties, includes a unimorph type diaphragm. The unimorph type diaphragm is defined by adhering a substantially square piezoelectric element onto a substantially square metal plate, the shorter sides of the diaphragm are supported on the supporting portion provided within the two opposing side wall portions of the case, the clearance between the remaining two sides of the diaphragm, and the case is sealed with a resilient sealing agent. The case is adhered on the substrate having external electrodes, the metal plate is connected to the external electrode with a resilient conductive paste, and the surface electrode of the piezoelectric element is connected to the external electrode with a resilient conductive paste. In this arrangement, the reliability of connection between the diaphragm and the external terminals on the substrate against the impact is greatly improved.

A piezoelectric electro-acoustic transducer is constructed such that adherence of a piezoelectric diaphragm to a casing is easily performed, a sufficient supporting strength is achieved, and the piezoelectric diaphragm is supported while hindrance of vibration thereof is minimized. This piezoelectric electro-acoustic transducer includes a piezoelectric diaphragm constructed by adhering a piezoelectric ceramic plate having front and back surfaces including electrodes, onto a metallic plate, and a case in which the piezoelectric diaphragm is accommodated by fixing the peripheral portion thereof with an elastic adhesive. Support portions for supporting the peripheral portion of the piezoelectric diaphragm are provided in the case, and a supporting surface having an arcuate cross-section is provided on the supporting portions so that a center of curvature of the supporting surface is positioned near a lower surface of the peripheral portion of the piezoelectric diaphragm.