Improved Earphone Enclosure for Communications in Noise

Abstract

In this paper, earphone enclosures are described embodying an improved acoustical network for enhanced noise reduction and efficient performance for an earphone. The network uses two chambers; one adjacent to the ear and the other contained in a re-entrant expanded portion of the enclosure. The two chambers are connected by parallel passages defining predominantly a resistance and an inertance. It is shown that this form of network is more effective than an arrangement of inertance and resistance in series. Cushions filled with nonfluid gel provide high wall impedance for good noise attenuation and good conformance with circumaural contours of the bead. Values of noise attenuation are given, measured by artificial head and by psychoacoustic methods. Performance of a typical earphone in the enclosure is shown.