Abstract: The present disclosure relates to a short-range communication device (10, 10?, 5 10?) for a personal protective equipment or a personal protective device (200, 210, 220, 230) comprising a transmission unit (20, 20?, 20?) for wirelessly transmitting a voice signal of a user (100, 110, 120, 130, 140, 150, 160) to a receiving unit (40,40?, 40?) over a predetermined distance such that a communication channel is established between the transmission unit (20, 20?, 20?) and the receiving unit (40, 40?, 40?) so that a user (100, 10 110, 120, 130, 140, 150, 160) can hear the voice signal. The present disclosure further relates to a short-range communication system comprising at least two short-range communication devices (10, 10?, 10?) according to the present disclosure and to a method of establishing a short-range communication between such devices (10, 10?, 10?).

Abstract: A damper containing magneto-rheological (“MR”) fluid and a plunger lies between and is mechanically coupled both to a fixture and a vibration source. The plunger has a head immersed in the MR fluid. Annular magnets circumscribe the damper and produce a magnetic field surrounding the damper. A tubular shielding sleeve composed of magnetically impermeable material surrounds a portion of the damper. The sleeve is mechanically coupled both to the fixture and the vibration source by springs, and can translate relative to the damper to affect the strength of the magnetic field acting on the MR fluid surrounding the plunger head. The sleeve oscillates responsive to vibration of the vibration source and controls the viscosity of the MR fluid surrounding the plunger head in proportion to the amplitude of the sleeve's oscillation. The resonant frequency of the sleeve is adjusted to approximate the fundamental resonance of the fixture.

Abstract: A fixture is isolated from the transmission of vibration emanating from a vibration source by a damper containing magneto-rheological (“MR”) fluid and a plunger mechanically coupling the damper and the fixture. The isolation apparatus is mechanically coupled to the vibration source. The viscosity of the MR fluid contained in the damper is controlled by a magnetic field produced by the vibration of an isolation system responsive to the vibration of the vibration source. The resonant frequency of the isolation system is adjusted to approximate that of the fixture.

Abstract: This invention presents a novel means to passively achieve a compact moving-coil actuator with a very low natural frequency. The diaphragm and voice coil are mounted in a sealed enclosure from which the air is partially or completely evacuated. This reduces the air spring effect. The diaphragm is supported by a non-linear, buckling, or collapsible support apparatus. By taking advantage of the non-linear stiffness properties of such structures, the stiffness of the actuator can be designed to be small at the operating point, which when combined with the moving mass, yields a low natural frequency.

Abstract: A virtual sky hook vibration isolation system provides reduction of transmissibility at resonance without significantly increasing high frequency transmissibility. Isolation is achieved passively and without the need for an inertial reference frame. Design of the primary and secondary suspension systems is performed concurrently to achieve the desired performance. The primary suspension affords the necessary static deflection properties and high frequency isolation. The secondary system couples to the system at resonance and provides damping to the dynamic response. This combination yields the isolation benefits of the skyhook damper concept. The penalty for this performance is the necessity of a secondary spring-mass-damper device. However, results indicated that good performance can be achieved using a relatively small secondary mass (5% of the primary mass).