A hinge assembly includes a base, a joint member, a pintle, and a coiling spring. The device may determine the level of blood constituent, may use this level for monitoring andor to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system. Furthermore, a cap member is located between the sound receiving member and the semiconductor substrate to cover the second surface of the semiconductor substrate. In addition, the program is operable to generate an inverse model of the playback system in the form of a digital filter. The conductive pattern is electrically connected to a variable power supply.