Page 18 - Occupational Health & Safety, March 2019

HEARING PROTECTION
Refreshing on the Basics of Noise and Hearing Conservation
Understanding what the rules are is only half of the battle with noise. The other half is assessing noise levels and utilizing effective controls.
BY ANDREW J. GOODWOIN ccupational noise exposure and hearing conservations programs can be one of the most elusive and oftentimes one of the most challenging programs to manage in the in- dustrial setting. As safety professionals, we need to become more aware and better versed in occupational noise exposure and how it affects diverse workforces,
but first, let’s look at the numbers.
According to the Occupational Safety and Health
Administration, more than 20 million workers are ex- posed to hazardous levels of noise at work. Employ- ers were cited nearly $1.5 million in federal OSHA citations in 2017, and workers’ compensation payouts cost another $242 million.
Unlike other injuries, hearing loss is hard to see and diagnose with the naked eye. Its effects are eas- ily masked and largely unrecognized until late in a worker’s career, when he or she is sitting at home and a neighbor has to ask the person to turn down the television.
In 2010, the Bureau of Labor statistics reported that 12 percent of all reported illnesses were related to occupational hearing loss, which equates to more than 18,000 workers who experienced significant hearing loss related to work.
Safety professionals must recognize the significant impact hearing conservation has on an employee. Most bones will heal, lacerations can be stitched, but once hearing is lost, it’s gone forever. As the next gen- eration of workers enters the workforce, we need to take a step back and look at how we manage hearing conservation and industrial noise exposure by getting back to the basics.
The Tipping Noise Scales
So, what is noise? To understand noise we first have to understand sound. Sound, as defined by Merriam- Webster’s Dictionary, is mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (such as air) and is the objective cause of hearing, see Table 1. Noise,conversely, is de- fined as any sound that is undesired or interferes with one’s hearing of something.
Measured in decibels, so appropriately named after the telecommunication pioneer Alexander Gra- ham Bell, noise is gauged utilizing units of sound pressure. There are three commonly used weighting scales for measuring decibels in industry. They are the A, C, and Z weighting.
The “A” weighted scale, which is abbreviated as dBA, has been adopted by OSHA as its weighting is thought to provide a rating of industrial noise that indicates the injurious effects such noise has on hu- man hearing, according to the OSHA Technical As- sistance Manual, 2013. “A” weighting follows the fre- quency sensitivity of the human ear at low levels. This is the most commonly used weighting scale, as it also predicts quite well the damage risk of the ear. Sound level meters set to the A-weighting scale will filter out much of the low-frequency noise they measure, simi- lar to the response of the human ear.
“C” weighting (dBC) is more flat among the ma- jority of frequencies with drop-offs at the higher and lowest frequencies. “C” weighting is typically not used for industrial noise but does have implications when conducting peak sound level surveys.
Last is the “Z” weighted scale, or “Zero” Weight. It is used when surveying total noise and has zero weighting, as the name would imply. The “Z” scale is rarely used in industrial safety applications but is use- ful during total noise evaluations.
The trivia question always arises on the “B” weight- ing. “B” weighting follows the frequency sensitivity of the human ear at moderate levels, used in the past for predicting performance of loudspeakers and stereos, but it is not used for industrial noise, so in short is not used in industry. Most of the time it is left out.
The Noise on the Regulations
Next, let’s discuss rules and regulations. There are three major noise standards primarily maintained by OSHA, the National Institute for Occupational Safety and Health, and the American Conference of Govern- mental Industrial Hygienists (ACGIH). In the spirit of compliance programs, we will be looking only at OS- HA’s 29 CFR 1910 Subpart G for Occupational Noise Exposure. Specifically, let’s look at occupational expo- sure limits set by OSHA. First is the Action Level (AL) of 85 dBA over an eight-hour time weighted average (TWA). This is the level at which it is estimated that 50 percent of the population will experience some hear- ing loss. When an employee is exposed at the Action Level (85 dBA eight-hour TWA), the employer is re- quired to provide at no cost to the employee:
16 Occupational Health & Safety | MARCH 2019
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