Abstract: An articulating supporting bracket for a surgical tissue stabilizer comprises a series of elements joined to one another by articulating ball-and-socket joints. A flexible cable extends through passages in the elements, and, when tightened, causes the balls and sockets to lock together frictionally. The ball of each joint fits into its socket by an interference fit, whereby the ball and socket of each joint engage one another over an area of contact when the cable is tightened, thereby providing a strong, rigid support for the tissue stabilizer.

Abstract: An ear defender having one or more microphones (1) for detecting the sound level in the proximity of the wearer's ear, one or more speakers (4) for generating a noise reduction signal within the earshell, and a digital feedback controller (W) for generating a feedback signal derived from the output of the microphones and for applying said feedback signal to the speaker inputs, and estimation means (F') for providing an estimation of the earshell transfer function and subtracting from the input to the feedback controller a signal representing the estimated electroacoustic transfer function of the system. The operation of the digital feedback controller may be controllable by the output of a computational circuit (C) operable on the difference between the microphone output and the feedback controller input modified by a model (F") of the electroacoustic transfer function.