Improved Earphone Enclosure for Communication in Noise

Earphone enclosures are described which embody 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 reentrant expanded portion of the enclosure. The two chambers are connected by parallel passages, one defining predominantly a resistance and the other 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 improved noise attenuation and conformance with circumaural contours of the head. Values of noise attenuation are given, measured by artificial head and psychoacoustic methods. Performance of a typical earphone in the enclosure is shown.