Some Improvements in Ear Enclosures

Attenuation of ear enclosures suffers limitations owing to resonance between earcup mass and compliance of cushions and the circumaural flesh. Worthwhile improvements in attenuation at this frequency and below are obtained by selectively coupled volumes (Helmholtz/Absorbers) tuned to this resonance. If the unwanted resonance falls below the communication spectrum of interest, then the added volumes produce no lowering of acoustical impedance load to the headphone transducers. A jel‐filled cushion is described. Since the jel does not escape through small holes or tears, it may be contained in an envelope of thin, limp plastic material. A special cross‐sectional configuration permits the cushion to conform to the circumaural region with little or no stretching of the envelope material, thus retaining the soft jel properties. [Work supported by the U. S. Army Electronics Command.]