Perhaps because it is invisible, sound is an often-overlooked
safety challenge in industrial workplaces. Whereas the physical dangers
from visually identifiable items such as forklifts or fabricating equipment are
obvious and immediate, sound-related danger tends to be of a less-tangible
and longer term nature, making it easier to ignore.
Excessive noise is a surprisingly widespread issue. The Occupational Safety
and Health Administration (OSHA) estimates that more than 30 million
U.S. industrial workers are exposed to hazardous levels of noise each year.
Employees in these environments aren’t just less efficient at their jobs,
they can suffer long-lasting damage leading to permanent hearing loss and
potentially exposing their employer to workman’s compensation claims.
Harmful noise levels are common in facilities with assembly and machine
tool operations or process equipment such as pumps, compressors and
blowers. They are also widely found in areas using material handling
equipment like conveyors and fork trucks or the regular usage of power hand
tools like saws, grinders and drills.
Keep it below 90 decibels
So how loud is too loud? According to OSHA regulation 1910.95, employers
must limit employee noise exposure to 90 decibels (dB) or less on an 8 hour
time-weighted average basis. To put that in perspective, a motorcycle at about
25 feet away produces noises of about 90 db, while a live rock concert rings
in at about 110 db.
Common noise control solutions
In an ideal scenario, excessively loud equipment can be redesigned or
replaced with newer, quieter machinery. However, the real world of industrial
facilities management is far from ideal. The cost and the availability of
quieter equipment can make replacement impractical, if not impossible.
In some instances, noisy machines can be modified to reduce or eliminate
noise-producing vibration. Adding
isolation pads or vibration dampeners
are both common ways of doing that.
Additionally, some machines can be
encased in sound absorbing enclosures
or materials. Unfortunately, neither
of these approaches are guaranteed to
be successful and, in some cases, they
may be impractical to implement.
Other situations will call for noise
reduction barriers to be placed
between the offending equipment and
the affected employees. This typically
consists of rigid, insulated walls or
partitions strategically placed to block
the path of transmitted sound waves,
and absorb and scatter them, reducing
the total sound power level that
actually reaches the affected employees.
If the excessive noise cannot be reduced to proper levels with either of
the aforementioned methods, employees will often wear personal hearing
protection, such as earplugs or ear muffs (either passive or noise canceling).
Earplugs and earmuffs can provide effective protection, but are only useful if
actually worn and fitted properly.
Personal hearing protection that does a good job of shutting out noises
doesn’t only keep out the bad sound – it can deter audible communication
between employees, creating potentially dangerous situations. Additionally,
in a facility where hearing protection is required, regular hearing testing of
affected employees is mandated by OSHA.
A new, proven method to control noise
Instead of installing traditional rigid, permanent walls for sound attenuation, a
new solution is quickly gaining popularity – industrial curtain walls. Specific
models of industrial curtain walls, which are composed of flexible materials,
can actually provide substantial noise reduction of up to 25 dB. And because
they aren’t permanent walls, they can be installed quickly and easily, then
reconfigured if the needs of a facility change.
Acoustic curtain walls typically consist of two layers of a woven, coated
fabric surrounding one or more layers of various insulating materials. These
materials might include fiber batting (polymer or glass), open cell foam, or
densified “loaded” vinyl or other flexible polymer sheet material.
Each of these components plays its own important role in reducing sound
levels impinging on the curtain surface. For instance, the mass loaded vinyl
sheet in a sound curtain is more effective in reducing lower frequency noise
than the other components (low frequency sound is best absorbed or deflected
with high density solid materials). Fiber batting is effective in reducing sound
at mid to higher range frequencies. Open cell foam (like a viscoelastic) will
also offer noise reduction over a range of frequencies, but care must be taken
to make sure the foam used is effectively treated for flame retardance.
The interior core of a typical sound curtain will consist of a layer of sound-dampening, loaded vinyl and a layer of antimicrobial polyester batting as an
additional sound buffer that also serves to fill out and maintain the body of
the panel. The most advanced curtain walls will have a core captured between
two outer layers of 18-oz flame retardant vinyl.
Typically, the loaded vinyl side of the
core is positioned facing the offending
noise source, between the source
and the desired ambient sound area.
Once installed, the wall acts to trap
the sound in a specific area and limits
the migration of noise to the ambient
Not only can these fabric curtains
be very effective for noise path
insulation, they can be used for noise
source insulation. For example, noisy
machines can be wrapped in flexible
acoustic curtains, like a blanket. They
can also be attached to a close quarters
support frame around the equipment.
Solution to Control Facility Noise