Total Noise Exposure
Thoughts on Controlling Noise on (and off) the Job
BY JOHN C. RATLIFF
There are two significant concepts in noise con- trol: engineering controls and total noise expo- sure. It is also important to remember that there
are both occupational and environmental exposures
to noise; many IH practitioners tend to ignore the off-
the-job exposures. This is a mistake: it’s important for
us to help people protect their hearing, both on and off
the job. Still, we can do a lot to control noise at work,
and many simple, effective interventions are often
Engineering controls have been the topic of intense discussion for years. Many people think that engineering controls are
always terribly expensive, which is not necessarily the case, as
shown by the scenario below.
Easy Engineering Controls
I work for a company that provides high-purity chemicals to
the semiconductor industry. We use drum rollers to condition
55-gallon chemical drums by rolling them with fluid so we can
remove contaminants. This procedure helps maintain chemical
purity. One day, I identified a drum roller that was too noisy.
After ensuring that production workers were aware of the hazard, and wearing proper hearing protection, I turned the drum
roller over to maintenance.
Months later, as I initiated a ventilation study of the area, I
got a good look at the drum roller (see Figure 1). Only one of
the screws holding its sheet metal sides was in place—the rest
were missing—and it had a loose clamp as well. These were the
reasons why it was so noisy.
I had not looked closely at the drum roller for several reasons.
For one, it was in use at the time of the high noise readings, and
in a clean room. I was told that it was “worn out” and needed
replacement. And, like the rest of us, I had a lot of other things
going on. Now, the fix looked easy. Simply replacing the screws
in the metal side, muffling the air exhaust and using some lubrication produced dramatic results. The resulting noise reduction
was down from 113.3 A-weighted decibels (dBA) to 88.7 dBA on
high speed and 80.8 dBA on low speed. Our work on the air muffler and side screws as well as our understanding that the drum
roller had a speed governor (air pressure) helped greatly. Simple
maintenance measures like these represent effective, inexpensive
engineering controls. I should have considered these sooner.
This is just one example of the many noise-related situations
I have encountered over the years. I have come to understand
that the ear has not been given the credit it deserves, nor has
it been protected as it should be. We are dependent on sound,
and yet unwelcome sound in the form of noise is ubiquitous. In
many industries, noise exposure is difficult to gauge, and protecting workers is even more challenging.
Noise Control in Construction
A few years ago, I was the EHS person for a construction project
that had a multi-employer work site with many contractors. I
wanted to understand the potential noise exposures for contractors in the area to determine whether workers needed hearing
protection. Because I was working off site, I asked another safety
Figure 1. This drum roller was excessively noisy until it was
lubricated, the screws put into place, and a muffler placed on
the air line.