(a) to modify the source to reduce its
(b) to alter or control the
transmission path and the environment so as to reduce noise level reaching the recipient,
(c) to provide the receiver with
personal protective device.
2.1 Control of Noise Source by
The source may be a single or
multiple of mechanical devices that emit acoustical energy. Due consideration on acoustic
matter during the design stage of the mechanical equipment will definitely minimize the
noise problem. The improvement techniques include the following:
(a) reduction of impact forces,
(b) reduction of speed and pressure,
(c) reduction of frictional
(d) reduction of noise leakage, and,
(e) isolation of vibrating elements.
2.2 Noise Control in Transmission
The next line of defense is to set
up devices in the transmission path to block or reduce the flow of sound energy before it
reaches the receiver. This can be done in several ways:
(a) to absorb the sound along the
(b) to deflect the sound in some other
directions by placing a reflecting barrier in its path,
(c) to contain the sound by placing
the source inside a sound-insulating box or enclosure.
2.3 Protecting the Receiver
When physical exposure to intense
noise fields is unavoidable and none of the measures mentioned above is practical, then
measures must be taken to protect the receiver as a final resort. The following two
techniques are commonly employed.
(a) Alter work schedule
In order to limit the amount of
continuous exposure to high noise levels, it is preferable to schedule an intensive noisy
operation for a short'. interval of time each day over a period of several days rather
than a continuous 8-hour run for a day or two.
Inherently noisy operations, such as
street repair, factory operation and aircraft traffic should be curtailed at night or
early in morning.
(b) Ear Protection
Ear plugs and other ear protectors
are commercially available. They may provide noise reductions ranging from 15 to 35 dB. It
should be aware that protective ear devices do interfere with speech communication and can
be hazardous when warning calls from a routine part of the operation.