The adaptive system and method for ultrasound sensing comprises re-evaluating over time the detection threshold for predetermined sensing positions along the scanning direction to cope for the static target and environment changes at the sensing positions. The labyrinth seal design including a plurality of features configured to open and close radial clearances in response to relative axial movement between a stationary component and a rotating component. The server system of the social network identifies one or more of the members of the preferred calling group as being one or more members of the social network.