To combat the threat of noise-induced hearing loss posed by intense noise environments, hearing protection devices (HPDs) have been utilized in U.S. industry since the 1950s, although their use was not widespread until promulgation of the Occupational Health and Safety Act of 1971. When properly selected and used, conventional HPDs offer an effective means of reducing the incidence of occupational hearing loss and noise annoyance, although they are not a panacea. In many industrial situations where speech communications and signal detection are necessary, workers complain that HPDs compromise their abilities to hear desired sounds. Recent litigation of a few industrial cases has implicated HPDs in accidents in which workers were injured when they did not hear a warning sound. This paper provides guidance for the proper application of HPDs in industry and reviews their effects on a worker's hearing in industrial noise. Also covered are several new technologies in HPD design (active noise cancellation, active sound transmission, frequency selectivity, adjustable attenuation, amplitude sensitivity, and uniform attenuation) which are aimed at improving the worker's ability to hear while providing adequate protection.