Abstract: A tri-axial vibration isolation device having: a passive isolation assembly including a first frame, a plurality of passive lateral isolators supporting the support frame on the base, and a plurality of passive vertical isolators; and an actuator assembly including a second frame, a vertical actuator arranged between the load and the second frame, and a plurality of lateral actuators arranged between the second frame and the passive vertical isolators. The actuators can be piezoelectric elements that change their thickness in response to an electrical signal. The lateral actuators are arranged in oppositely poled pairs. An accelerometer or other sensor provides information to a controller that controls the actuators.

Abstract: The invention described herein is a low-mass, light-weight sound generator with particularly good performance at mid and low audio frequencies. It is expected to find principal use in applications where mass is of crucial importance. It is capable of delivering the high acoustic levels, as required for sound generation or active sound control. The present invention uses a generally planar acoustic membrane as a diaphragm, the diaphragm being in tension and attached at its outer edge to a support frame which provides a soft boundary condition to the acoustic diaphram. In a preferred embodiment, the support structure is an inflatable toroidal tube of rubber or rubber-like material. A polymer membrane is attached to the support structure by heat sealing the membrane in place. A voltage is applied to a piezoelectric bender-type actuator, which imparts axial displacement to a region of the diaphragm, causing resonance of the diaphragm in the desired frequency range.

Abstract: Various embodiments of low-mass sound generators each having a wide frequency band are disclosed. In some embodiments, the acoustic transducer acting as the sound generator is constructed of four layers of PVDF film. The top and bottom bi-laminate members are separately formed in a pre-curved manner to form a rippled geometry.

Abstract: Various embodiments of low-mass sound generators each having a wide frequency band are disclosed. In some embodiments, the acoustic transducer acting as the sound generator is constructed of four layers of PVDF film. The top and bottom bi-laminate members are separately formed in a pre-curved manner to form a rippled geometry.

Abstract: Various embodiments of low-mass sound generators each having a wide frequency band are disclosed. In some embodiments, the acoustic transducer acting as the sound generator is constructed of four layers of PVDF film. The top and bottom bi-laminate members are separately formed in a pre-curved manner to form a rippled geometry.

Abstract: A monolithic piezoelectric accelerometer of the longitudinal type having a ass element, a piezoelectric accelerometer sensor element and electrodes interconnecting the mass and sensor elements, in which the mass and sensor elements are formed as a monolithic structure. Included is the method for making the monolithic piezoelectric accelerometer.

Abstract: The present invention is a controllable surface based upon a 1:3 piezoeleic composite (sometimes referred to as a 1-3 composite or a 1/3 composite). The 1:3 piezoelectric composite has a first planar electrode plate, a first plurality of piezoelectric rods fixed to and extending normally from the first planar electrode plate, a second plurality of piezoelectric rods fixed to and extending normally from the first planar electrode plate, and a second planar electrode plate, coupled to the first plurality of piezoelectric rods and decoupled from the second plurality of piezoelectric rods, essentially parallel to and opposing the first planar electrode plate. The first plurality of piezoelectric rods act as actuators, and urge the first planar electrode plate in a direction normal to said plate in response to an actuator signal (applied as a bias between the two planar electrode plates).

Abstract: An active impedance modification device or arrangement enables the interaction of sound with a structural surface to be controlled, e.g., so that, reflections from that surface (which can be the hull of a submarine) are substantially reduced or eliminated. The device comprises a coating comprising an inner driver transducer layer in contact with the structural surface an outer receiver transducer layer which receives the sound, in combination with a variable gain, variable phase shift amplifier connected between the interface of the outer layer with the sound carrying medium (e.g., water) and the interface between the second layer and the structural surface. Reflections are reduced by setting the gain and phase shift of the amplifier to simulate the input impedance of the sound carrying medium.