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Despite numerous technological advances in the metalworking industry over the past twenty years, noise continues to be a major hazard, with levels at typical shops easily exceeding 100 dB.

Excessive noise, according to a recent World Health Organization study has "many adverse effects, including elevated blood pressure, reduced performance, sleeping difficulties, annoyance and stress, tinnitus, noise-induced hearing loss (NIHL) and temporary threshold shift." Of these, noise-induced hearing loss is the most significant. Damage to the delicate hearing mechanisms of the inner ear caused by excessive noise accumulates slowly over time and cannot be repaired: noise-induced hearing loss is permanent.

It is also 100 percent preventable. OSHA's Occupational Noise Exposure Standard and Hearing Conservation Amendment (29 CFR 1910.95) stipulates that employers "shall administer a continuing, effective hearing conservation program" when worker exposure levels "equal or exceed an eight-hour time weighted average sound level (TWA) of 85 dBA."

In this article, we will summarize the key elements of an OSHA-approved Hearing Conservation Program.

NOISE MONITORING/AUDIT

Before an effective hearing conservation program can be established, you need to accurately characterize the noise environment and identify affected employees. OSHA requires monitoring when noise levels equal or exceed 85 dBA TWA (Time Weighted Average at 8-hours), including all continuous, intermittent and impulsive sound. A good rule of thumb is that if you must raise your voice to be heard by someone an arm's length away, the noise level is probably hazardous.

Monitoring requires sound level meters which sample area noise levels, and dosimeters which record an individual's noise exposure. While area sampling provides a good understanding of general noise levels throughout a facility, personal sampling documents a worker's complete exposure during the course of their work day. Re-measurement is required when noise levels change "significantly," though it's a good idea to remap affected areas annually regardless of change.

Posting a "noise map" of a facility can help give workers a visual reference to sites where hearing protection devices (HPDs) must be worn. Posting specific decibel levels in work areas is also an effective way to identify the need for HPDs and help workers select the right protector for their application.

Concurrent with initial or annual monitoring, a full program audit should be conducted. This should focus not only on noise hazards but on a top down review of the management, administrative, and material resources available to control them. Studies have shown, for example, that employees who fail to wear hearing protectors or who tend to skip hearing tests, tend to work for supervisors who do not take hearing conservation seriously. An audit can help make sure the management structure is in place to enforce program requirements. (A free guide of practical tips, "Best Practices in Implementing a Hearing Conservation Program," can be downloaded from www.howardleight.com)

AUDIOMETRIC EVALUATION

OSHA requires all new employees to undergo an audiometric test within six months of employment. All noise-exposed workers must also be tested on an annual basis. Individual results are compared from year to year to determine if hearing has remained stable.

Audiometric testing must be conducted by a trained professional, and can be done in-house or outsourced to industrial clinics and audiology practices. Many practices offer mobile testing services that are very economical, and can work around employees' schedules to minimize worker downtime. One source list of competent mobile testing services is maintained by the National Hearing Conservation Association (303/224-9022 or nhca@gwami.com).

A good idea is to use an audiometric testing provider who can combine required employee training with the annual audiometric test. One-on-one training at the time of testing is often more effective than group training. Also, make certain your testing service provides the required baseline comparisons, and that the follow-up reports are understandable.

While audiometric technicians can administer an audiogram, only audiologists, otolaryngologists and physicians may interpret the test results. Often these providers can send out any notifications as required by the OSHA standard. Research has shown that when employees receive copies of their audiograms or explanations of the results at the time of testing, rates of noise-induced hearing loss in that workforce decrease.