Patent ID: 8670586

Claim:
A headphone comprising: an electroacoustic transducer; a shell enclosing a back side of the electroacoustic transducer to define a back cavity, a first opening and a second opening through the shell each coupling the back cavity to an outer surface of the shell; and a plate attached to the shell, the plate having a bottom surface abutting the outer surface of the shell, and a top surface opposite the bottom surface, wherein the plate includes: an exit cavity defined by side walls interior to the plate, an upper aperture in the top surface of the plate, and a lower aperture in the bottom surface of the plate, the lower aperture corresponding in dimension to the first opening through the shell and aligned with the first opening through the shell, and a channel forming a half-tube in the bottom surface of the plate; wherein the half-tube begins at a point aligned with the second opening through the shell and ends at an aperture through one of the side walls of the exit cavity; the channel and the outer surface of the shell together form a reactive acoustic port from the back cavity 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.