Despite decades of regulations, noise-induced hearing loss continues to be one of the most prevalent workplace injuries in many industries. While damage to hearing is the well-known result of overexposure to hazardous noise, there are a number of other physiologic and behavioral effects of hazardous noise. In this interview with Brad Witt, audiologist and Director of Hearing Conservation at Honeywell Safety Products, we discuss some of those other effects, their causes and solutions.
Hearing loss due to loud noise exposures has been a well-documented occupational hazard. Do we know what noise levels cause hearing damage?
Most occupational hearing loss occurs as a result of prolonged exposure over time – not just a single loud event. Experts have defined a population average of 85 decibels (dB) over an 8-hour workday as a maximum daily exposure limit; so many regulations use that criterion. But it is not a hard brick wall, rather just a line in the sand. Some people (by some estimates, 5-12% of the population) will suffer some permanent impairment in prolonged exposures even below 85 dB. Many proactive employers will offer hearing protection in any area where average noise levels exceed 80 dB, just to accommodate workers who may be more susceptible to noise damage.
One rule of thumb to determine if the noise is hazardous is a shouting criterion: if you must shout to be understood over the background noise by someone just an arm-length away from you, that noise is likely hazardous, close to that 85 dB criterion.
Hearing loss has such a slow progression over time. How would a worker know if their hearing is being damaged?
The damage to hearing progresses so slowly that it’s difficult for most workers to detect the difference from one month to the next. Regular audiometric testing is one of the best methods of early detection for any shifts in hearing. That audiogram helps determine if the hearing loss is progressing faster than what would be expected from normal aging.
The early warning signs of noise damage are subtle: the clarity of conversation will be affected before the loudness. One of the most common complaints from those suffering from noise-induced hearing loss is, “I can hear you speaking, but I just can’t understand.” This is especially noticeable in background noise, such as a restaurant or meeting place. One of the other telltale signs of noise damage is tinnitus, or ringing in the ears. A little bit of ringing is normal in everybody – it comes and goes intermittently. But a worker with noise damage will often have continual ringing in the ears. It can be disruptive to sleep and solitude, and annoying for life. Temporary ringing after a loud noise exposure can be the ear’s method of warning us the noise was too loud. But if we are exposed to loud noise day in and day out, the temporary ringing becomes permanent.
Are there other effects of hazardous noise exposure?
Hearing loss and tinnitus are the most common, but there are host of other physiologic and behavioral effects of loud noise exposure.
The psychological health of some workers is affected, and in certain cases, the family and friends are too. Isolation, self-esteem and depression problems can be observed.
The Canadian Centre for Occupational Health & Safety provides a good resource describing many of these effects. In the workplace, the auditory effects include difficulties with oral communication, warning signal detection, and job performance, particularly on high-vigilance tasks. In many jobs, communication with co-workers and warning signal detection are critical to the operation, so good hearing means better productivity and safety.
High noise exposures in the workplace have also been correlated to non-auditory effects like cardiovascular function. One Canadian study determined that heart problems were 2-3 times more likely in workers exposed to high noise. Fatigue, anxiety, and insomnia have all been correlated to high noise exposures. These symptoms are not always predictable in a cause-effect relationship, but higher correlation suggests noise plays some contributory role.
What can the employer/employee do to mitigate these kinds of effects?
Proper hearing protection, both on- and off-the-job, reduces or eliminates nearly all of these effects. The ideal would be to eliminate noise at the source through engineering controls. But when that is not feasible, properly-fitted hearing protection is an excellent mitigator against hazardous noise. Workers who consistently wear hearing protection can expect to maintain their good hearing throughout their lifetime, all other things being equal.
The key words with wearing hearing protection are consistently and correctly. Fit-test systems are available from several manufacturers that actually measure in the field how much noise is being effectively blocked by a hearing protector. These systems can alert the worker, for example, if an earplug is not inserted properly or is the wrong size. And consistency is critical for proper protection, both on-the-job and off. For some workers, recreational noise exposures may be just as hazardous as those found in the workplace. Loud music, hunting, chainsaws, power tools, motor sports – they can all take their toll on hearing just as easily as the grinder at the workplace. But for those recreational noise exposures, there is often no warning signage as there may be at work; it’s just up to the individual to take responsibility for their own hearing protection.
While hearing losses due to loud noise, and the non-auditory effects of noise, are often painless and permanent, they are also very preventable with consistent use of proper hearing protection.