Noise has been recognized as an occupational hazard since the 1700's. Noise is considered unwanted sound and is a by-product of many industrial operations. Sound results from pressure changes in air due to vibration. Overexposure to noise results in hearing loss. The extent of hearing loss depends upon loudness and duration of exposure. Noise-induced hearing loss can start out as a temporary effect from short-term exposure and recovery occurs after removal from exposure. This effect is experienced by many people after attending a loud concert. This reversible effect is called a Temporary Threshold Shift (TST). Repeated and chronic overexposure to noise can result in permanent hearing loss, called a Permanent Threshold Shift (PTS).
Occupational hearing loss results in difficulty in hearing and communicating with coworkers, family members and the general public and feelings of isolation. In the workplace it causes reduced safety awareness and accidents, lack of perception of forklifts and warning alarms, and reduced productivity. Tinnitus, ringing in the ears, can also be experienced.
OSHA estimates that 30 million American employees are exposed to excessive workplace noise. Noise assessments are the most common industrial hygiene consultation conducted. It is widely acknowledged that noise-induced hearing loss can be reduced or eliminated through hearing conservation programs and engineering controls. Interestingly, the incidence of OSHA 300 hearing loss recordable cases is decreasing while workers' compensation claims are increasing. These scenarios are due to more stringent reporting requirements and earlier problem recognition. A 2005 University of Washington study found that most of the participating companies had substantial shortcomings in their hearing loss prevention programs.1 Beginning January 1, 2003, employers must record workers with an average hearing loss of 10 dB at 2000, 3000, and 4000 hertz and whose hearing level threshold after the change averages 25 dB or more at 2000, 3000, and 4000 hertz on the OSHA 300 hearting loss column. Before that time hearing loss was recorded when there was an average loss of 25 decibels at 2000, 3000, and 4,000 hertz (Hz). With recognized hearing loss, the employer must take protective measures, including requiring the use of hearing protectors for affected employees.
The Bureau of Labor Statistics recordable hearing loss reduction trend follows the timeline of more stringent reporting requirements. See Table 1. There has been a clear reduction in recordable cases over the past four years from the manufacturing sector.
(Table in full paper)
In some cases, earlier hearing loss identification has resulted in an increased occurrence of workers' compensation hearing loss claims. In the United States, different states have different hearing loss thresholds for workers' compensation partial and total disability, as well as positions on workplace causation or aggravation of pre-existing conditions. A Standard Threshold Shift does not automatically document the basis for a Workers' Compensation claim. Each state has developed compensability laws and requirements. Lack of exposure monitoring, hearing protection enforcement and audiometric test follow-up result in potential hearing loss being addressed less effectively than possible.