STOPPING A LITTLE NOISE CAN SAVE A LOT OF HEARING
Safety article by Harold Hough   

            I once asked a friend and retired Green Beret once about hearing protection during a firefight.  He had helped fight the Soviets in Afghanistan in the 1980s, the Iraqis in the 1990s and 2003, and the Taliban and Al Qaeda in 2002.  As I suspected, they don’t wear anything during a fight – they want to be sure they hear the bad guys.
            Fortunately, the last time I spoke with him, he showed no signs of deafness.  However, the odds are that he has already lost some hearing and that he will probably lose more over the next few.
            But, there is a big difference between the necessities of war and normal operations in mining.  While some mine workers insist that they don’t need ear protection, the fact is that the noise levels at mining operations will damage your hearing during the long run.  In fact 49% of male miners have measurable hearing loss by the age of 50.  Another study conducted by the National Institute for Occupational Safety and Health (NIOSH) indicates that 70-90 % of all miners have a noise-induced hearing loss (NIHL) great enough to be classified as a hearing disability by retirement age
            While we associate hearing loss with loud noises, research shows that exposure to lower levels of noise can seriously damage the ear.  Gradual hearing loss can be caused by multiple exposures to any source of excessive volume, such as home and vehicle stereos, concerts, nightclubs, and excessive noise in the workplace. The U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) states that exposure to 85 dB(A) of noise, known as an exposure action value, for more than eight hours per day can result in permanent hearing. Since decibels are based on a logarithmic scale, every increase of 3 decibels results in a doubling of intensity, meaning hearing loss can occur at a faster rate. For instance, 95 decibels can only be tolerated for 2 hours before serious damage can take place.  Therefore, gradually developing hearing loss occurs from the combination of sound intensity and duration of exposure.  (Note that the previous figures aren’t MSHA standards and only reflect OSHA studies)
            When the ear is exposed to high noise levels for a long period of time, the hair cells inside the cochlea degenerate and is less capable of sending signals to the brain.  That creates the long term hearing loss.
            So, what type of noise can cause hearing damage at a mine?  According to the Michigan Mine Safety and Health Training group, a quiet room has a noise level of 45 decibels.  An air track drill has a noise level of 115 decibels, which means it is transmitting 10 million times more noise energy to the ear and is capable of causing 10 million times more hearing damage.  A haul truck with a good cab has a noise level of 85 decibels, which 10,000 times more noise energy to the ear.  A rock crusher has 95 decibels and 100,000 times the noise energy.
            The good news is that hearing loss can be prevented by simple hearing protection, education and hearing prevention programs.  And, since a small increase in decibels can dramatically harm hearing, even a small decrease in noise can significantly reduce the chance of hearing damage.  Even a reduction of three decibels reduces the amount of noise energy entering the ear by 50%
Although MSHA recommends enclosed cabs for heavy equipment operators, there are other things that a mine can do to create small decreases in noise level.  Experts recommend that large metal surfaces inside heavy equipment cabs need to be covered with sound absorbing material to prevent reverberation.  Even putting old rubber conveyor belts on the floor of the cab can significantly reduce potential hearing damage.
            The Washington State Department of Safety and Labor recommend road surface treatment to reduce noise from heavy equipment.  For instance, a hard, rocky surface is nosier than many other surfaces.  The reason is not that the rock is naturally noisier when heavy equipment runs on it, but it is more likely to reflect noise rather than absorb it.   Interestingly enough, many dust control products, including water, will dampen the noise level.
            But training is also important – and not just training employees to keep their hearing protection on.  Studies have found that modern heavy equipment cabs are excellent noise protectors and much of the noise transmitted to the operator’s ears came from the time the cab door is open.  Consequently, keeping the cab door and windows closed dramatically improves the long term hearing protection for the operator.
Although mining is a critical industry, miners don’t have to sacrifice their hearing like soldiers may do in a firefight.  Very simple practices that reduce noise levels by even a few decibels will allow your employees to keep hearing for decades to come.