Abstract: A plate attached to the back shell of an earphone includes an exit cavity corresponding in dimension to and aligned with a first opening through the back shell. A channel in the bottom surface of the plate begins at a point aligned with a second opening through the back shell and ends at an aperture through a side wall of the exit cavity. The channel and the outer surface of the back shell together form a reactive acoustic port from a back cavity enclosed by the back shell to the exit cavity, the first opening through the shell forms a resistive acoustic port from the back cavity to the exit cavity, and the exit cavity couples the reactive acoustic port and the resistive acoustic port to free space without introducing additional acoustic impedance. In some examples, a water-resistant screen covers the upper aperture of the exit cavity.

Abstract: A plate attached to the back shell of an earphone includes an exit cavity corresponding in dimension to and aligned with a first opening through the back shell. A channel in the bottom surface of the plate begins at a point aligned with a second opening through the back shell and ends at an aperture through a side wall of the exit cavity. The channel and the outer surface of the back shell together form a reactive acoustic port from a back cavity enclosed by the back shell to the exit cavity, the first opening through the shell forms a resistive acoustic port from the back cavity to the exit cavity, and the exit cavity couples the reactive acoustic port and the resistive acoustic port to free space without introducing additional acoustic impedance. In some examples, a water-resistant screen covers the upper aperture of the exit cavity.

Abstract: A modular front panel system for circuit cards utilizes hinged, interlockable, first and second circuit-card-carrying front panels. Each panel has a hinge component, e.g. a pivot element) that can mate with the component on the other panel (e.g., a groove). The hinged arrangement permits the panels to be releasably secured to one another so as to form a card assembly unit. The hinged arrangement also permits the panels to be moved angularly with respect to one-another, thereby facilitating assembly and disassembly of the two hinge components without obstruction by components mounted on the circuit cards. This is particularly well suited to applications in which the circuit cards have surface mounted connectors that mate and electrically connect when the panels are moved angularly. Moreover, the hinge arrangement permits a panel to be readily added and interlocked with, or removed from, an existing card assembly in electrical equipment, without requiring replacement of the existing front panel.