[Ear protective plugs].

Abstract

The authors present results of studies of application of polyurethane foam to produce individual sound-absorbing ear plugs. In addition to physico-mechanical properties of the foam, the authors present its optimum prescribed composition, ensuring appropriate attenuation qualities, flexibility, softness and long -- lasting strain relaxation -- i.e. the conditions resulting in excellent filling of external auditory meatus, masking effect and utilization comfort. The efficiency of attenuation of sounds by the plugs, tested audiometrically by the method of auditory threshold shift in otologically healthy subjects ranges from 12.25 dB (250 Hz) to 29.75 dB (4000 Hz). No significant inflammatory reactions in external ear skin were found after 8 hrs of continuous wearing of ranges under the work conditions typical for the textile industry. The results demonstrate that the polyurethane foam, developed by the authors, are valuable ear protectors, of advantageous functional qualities.