Abstract: A magnetostrictive actuator comprises an assembly of at least two GMM rods (8, 9) spaced apart from each other on the same longitudinal axis, each rod being surrounded by a respective energising electromagnetic coil (10,11) 5 and being mounted between respective biasing permanent magnets (12, 13, 14), the assembly being mounted between mechanical pre-stressing means (20, 21) and a foot (3) adapted to couple the forces produced by the actuator into a surface.

Abstract: A hermetically sealed actuator design for absorbing and reducing the effect of sound or vibration energy from a vibrating surface. The device comprises a body (1) containing a magnetostrictive core (2-6) a reaction mass (7) for energizing the actuator by compression, and a bearing or lever system to control the movement of the reaction mass. The actuator has a foot (11) for receiving the vibration from the structure into the device and a sensor (13) for monitoring vibration levels. The device can also function as an audio transmitter whereby it vibrates the surface onto which it is mounted and can be used for audio trans-10 mission through the structure or noise and vibration reduction by driving the surface out of phase with the vibration received from the structure.

Abstract: A hermetically sealed actuator design for absorbing and reducing the effect of sound or vibration energy from a vibrating surface. The device comprises a body (1) containing a magnetostrictive core (2-6) a reaction mass (7) for energising the actuator by compression, and a bearing or lever system to control the movement of the reaction mass. The actuator has a foot (11) for receiving the vibration from the structure into the device and a sensor (13) for monitoring vibration levels. The device can also function as an audio transmitter whereby it vibrates the surface onto which it is mounted and can be used for audio transmission through the structure or noise and vibration reduction by driving the surface out of phase with the vibration received from the structure.

Abstract: A magnetostrictive actuator comprises an assembly of at least two GMM rods (8, 9) spaced apart from each other on the same longitudinal axis, each rod being surrounded by a respective energising electromagnetic coil (10,11) 5 and being mounted between respective biasing permanent magnets (12, 13, 14), the assembly being mounted between mechanical pre-stressing means (20, 21) and a foot (3) adapted to couple the forces produced by the actuator into a surface.

Abstract: An acoustic transducer comprises an active element which changes in length along a first axis in response to an audiofrequency input signal, the element being mounted between an inertial mass and a foot which in use engages a surface whereby audiofrequency vibrations produced by the active element are transmitted to the surface, characterised in that the foot is hingedly connected to the inertial mass and the active element is located between the foot and the mass such that the angle between the first axis and the surface is less than 90°, in use.

Abstract: An acoustic transducer comprises an active element (21) which changes in length along a first axis in response to an audiofrequency input signal, the element being mounted between an inertial mass (20) and a foot (24) which in use engages a surface whereby audiofrequency vibrations produced by the active element are transmitted to the surface, characterised in that the foot is hingedly (25) connected to the inertial mass and the active element is located between the foot and the mass such that the angle between the first axis and the surface is less than 90°, in use.