Abstract: A piezoelectric audio transducer suitable for underwater use comprises a piezoelectric ceramic plate within a housing having open front face and back faces exposing the front and back faces of the ceramic plate to ambient pressure. The ceramic plate can be supported in spaced relation from the housing by, for example, open cell foam, so as to be vibrationally isolated from the housing.

Abstract: A filter cartridge is described for use in a system to remove impurities from the air. The cartridge has a filter section which may provide tortuous air flow channels between an inlet and an outlet of the filter section. The filter section may be formed from a pair of adjoined sheets with at least one of the sheets having an internally directed raised pattern thereon. This raised pattern spaces the adjoined sheets. The adjoined sheets may be rolled-up into a spiral shape and are positioned in the cartridge with said sheets paralleling an air flow direction through said filter section. It is also contemplated that the raised pattern of the adjoined sheets provide linear air flow channels but ones which are less than three millimeters in height. Alternatively, the filter section may comprise an open pore sponge or foam. The cartridge may be provided with an inlet closure plate having openings therein so as to impart turbulence to incoming air.

Abstract: This invention relates to a strength member for a hose and to an improved combined fluid/electrical hose. The strength member of the present invention is a low stretch high strength natural or artificial fibre material which may be incorporated into the bore of the hose and fastened to a hose end termination connector at each end to limit stretch of the hose. In the improved combined fluid/electrical hose of the present invention, the electrical wire extends longitudinally and freely the full length of the hose without attachment to the inner hose wall. This combined fluid/electrical hose also including a strength member.

Abstract: A noise cancelling watertight transducer that converts sound wave to electromagnetic waves or conversely electromagnetic waves to sound waves comprises a hollow shell having curved walls mounted for movement in a resilient container. A freely movable inertial mass is located inside said shell. The inertial mass resists movement when a force is applied thereto. Signal translating means are incorporated therein consisting of either an electromagnetic device, a piezoelectric element or voltage potential senative element that is mounted in and connected with said shell and interacts with said inertial element. In response to appropriate signal some embodiments of the instant invention acts as a bidirectional device converting electrical signal to acoustical signal or conversely acoustical signal to electrical signal.