Since the inception of hearing conservation regulations hatched in the 1970's, efforts to stop noise-induced hearing loss always have been tied to a lagging indicator – namely, audiometric testing. If repeated audiometric testing indicates a progression of hearing loss among noise-exposed workers, then we know something is amiss in the hearing conservation program.
By relying on audiometric testing, intervention often begins after the damage has been done. Employers refit hearing protection or reduce the noise exposure only after an employee demonstrates a downward shift in hearing.
In the last decade, the Bureau of Labor Statistics reported rates of hearing loss in private industry as being nearly flat1 – not the hoped-for loss prevention that the 1983 Hearing Conservation Amendment was intended to inspire. At a workplace, this fact often is voiced in comments from safety managers: "We measure the noise, provide protectors, and test the hearing of the workers – and we still show shifts in hearing, year after year. What are we doing wrong?"
The disconnect occurs for several reasons. The published noise reduction rating (NRR), based on laboratory testing of 10 people under ideal conditions, often is a poor predictor of individual protection in the real world. Estimated noise exposures under the hearing protection for any given worker are usually wild guesses. Hearing protectors often compete with verbal communication, causing a disincentive for proper wearing. The only success metric defined in the regulation – audiometric testing – is a lagging indicator that takes years to indicate a problem. It all spells trouble for companies that are trying proactively to stop occupational hearing loss before it shows up as a recordable shift or compensation claim.
In a connected workplace, employees and supervisors accurately could know how much protection each worker achieves with a particular earplug or earmuff. Noise levels could be monitored real-time under the protector, and workers and managers could be alerted when exposures reach hazardous limits. Communication could be enhanced, not degraded, by the personal protective equipment (PPE).
In short, the hearing protector would document its own effectiveness.
The good news is that these technologies all are available in the workplace.
For decades, the safety manager's only tool for predicting protection levels from an earplug or earmuff was the NRR on the package. But hearing conservation professionals have long recognized that the NRR is not a good predictor of real-world attenuation.
Under current EPA regulations, the NRR is based upon ten people tested in an acoustic lab under ideal conditions. The hearing protector is fit on the subjects by the experimenter, and the subjects sit motionless in a chair for the duration of the testing. No head or jaw movements are allowed; the subjects wear the protectors for only a few minutes at a time and the discomfort of the fit is not considered in the testing process. With such a contrived test set-up, it is understandable that many hearing conservation professionals describe the NRR as "not really relevant" to real-world protection.
Fit testing of hearing protection allows a safety manager to measure the protection levels of hearing protectors in the field under real-world conditions. Several systems allow users to test the real earplugs workers normally use, fit just the way the worker normally inserts them. The resulting measurement needs no de-rating or adjustment to predict real-world protection; it is the real-world protection measurement. Workers walk away from their fit-testing knowing what a good fit feels and sounds like; managers have documentation of a good fit, adequate for the noise levels on-site.
Fit-testing now is accepted as a best practice in many hearing conservation programs. In a Best Practice Bulletin published by an OSHA Alliance of hearing conservation professionals, seven benefits of fit-testing of hearing protectors were defined.2 The bulletin endorses fit-test systems for their value in assisting to select proper protection, train workers in proper fitting techniques and re-fit workers whose audiometric results demonstrate a shift in hearing. Fit-test systems also provide valuable documentation that the employer has provided adequate protection and training for its noise-exposed workers. Rather than relying upon the lagging indicator of audiometric testing, fit-testing is a leading indicator that identifies a hearing protection problem months or years before it shows up as a recordable shift.
While fit-testing provides a snapshot in time regarding the protection levels of a hearing protector, there is no guarantee a worker repeatedly will fit the protector in that same manner. In-ear dosimetry, however, continuously monitors real-time protection levels under the protector, and alerts the worker immediately so that proactive measures can prevent hearing damage.
Technology that connects us to our surroundings has bloomed in the past decade. We can connect remotely to the heat or lighting in our homes. Personal sensors can warn us of hazards while we work, drive and even sleep. Many of these devices are wearable, giving us immediate feedback to our heart rate, quality of exercise or other biometric alerts.
In the noisy workplace, the connected worker wears protection that verifies its own efficacy. While traditional noise dosimetry takes measurements from a microphone mounted on the shoulder of a worker, in-ear dosimetry essentially inserts that microphone under the PPE (on the eardrum side of an earplug or under the ear cup of an earmuff). Real-time sensors alert the worker when noise levels under the PPE exceed safe exposures, and integrated dosimetry monitors the overall noise dose throughout the day. The worker and supervisor can be alerted long before the noise dose approaches hazardous levels.
The additional benefit of in-ear dosimetry is its ability to measure any "cheating" in the use of the protector. To hear critical sounds, workers sometimes remove their earplugs, or lift off their earmuffs for just a minute or two, assuming that a few minutes without protection "isn't a big deal." But it is a big deal.
In hazardous noise, small intervals of no protection quickly void long periods of adequate protection, due to the logarithmic scale used in measuring decibels. Fifteen minutes of cheating out of an eight-hour workday easily can decrease protection levels by one-half for the entire workday. Using in-ear dosimetry, if a worker removes the PPE for just a few minutes for any reason, the dosimeter will be reading high because it is capturing the ambient loud noise levels. An overexposure alert can be triggered not just for a poorly-fitted earplug or earmuff, but also for a protector that repeatedly is removed throughout the day, exposing the worker to short bursts of hazardous noise.
The biggest benefit from technologies like fit-testing and in-ear dosimetry is the elimination of surprises. No longer do employees suddenly show up with a hearing loss, several years into the audiometric testing program. Instead, these connected workers and their managers know on day one of employment whether their protected noise exposures are hazardous, and corrective intervention immediately can be implemented.
A noisy worksite filled with warning signals, radio communication and moving equipment gives a worker a ready excuse for not wearing hearing protection. "I would rather lose my hearing than lose my life," the rationale goes. The assumption is that earplugs and earmuffs isolate the worker from critical sound, and the worker must choose one or the other. But it's a myth to assume critical communication and hearing protection cannot co-exist.
In a NIOSH field study exploring why noise-exposed workers don't wear their hearing protection, the primary reason given was the workers' fear that it would interfere with communication and job performance.3 The problem especially is acute for workers with an existing hearing loss. For them, wearing earplugs or earmuffs produces a double hearing loss: the attenuation of the protector overlaid on their existing loss.
Fortunately, manufacturers have responded with a number of speech-friendly hearing protectors. Some electronic earmuffs are designed with amplification circuitry that makes speech easier to understand in intermittent noise. At safe noise levels, these earmuffs amplify the signal, allowing easy conversation while wearing the protectors. But when incoming noise levels above safe limits are detected, these immediately revert to a noise-blocking, passive earmuff to offer optimal attenuation.
New intelligent devices borrow technologies from military applications, where incoming sound from a communication radio is enhanced to make speech more audible, while background noise is electronically suppressed. Today's hearing protectors allow the noise-exposed worker to be protected but still connected. Technology integrated into the earplug or earmuff (like Bluetooth link, speech enhancement or impact noise reduction) provide the worker with situational awareness and communication.
In today's workplace, the connected worker uses smart technology to increase productivity without sacrificing safety. Technologies that measure real-world protection, PPE that verifies its own efficacy and hearing protectors that enhance communication connect workers to their job, their environment and their own safety awareness.
Brad Witt, MA, CCC-A, is the director of hearing conservation for Honeywell Industrial Safety. He holds a B.S. in communication disorders from Brigham Young University, and an M.A. in audiology from Northwestern University. He has served as president of the National Hearing Conservation Association (NHCA) and has presented more than 250 hearing conservation seminars on behalf of Honeywell Industrial Safety during the past eight years in 18 countries. Contact him by e-mail at [email protected]
1Martinez, L.F., "Can You Hear Me Now? Occupational Hearing Loss, 2004–2010," Monthly Labor Review, July 2012.
2OSHA/NHCA/NIOSH Alliance (2008). "Best Practice Bulletin: Hearing Protection-Emerging Trends: Individual Fit Testing." http://www.howardleight.com/images/pdf/0000/0404/AllianceRecommendationForFitTesting_Final.pdf
3Morata, T., "Issues Regarding Hearing Protection Device Use in Manufacturing and Mining," Journal of the Acoustical Society of America, 112(5):2295-2295 (Nov 2002).