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WAYNE TUSTIN
a President
■< Tustin Institute of Technology, Inc.
Santa Barbara, Calif.
Why Worry about noise and vibration? There are
several reasons. For one thing, they are often
warnings that a part will soon fail. In addition to
indicating failure, they may cause failure in ma
chines; under vibration, parts loosen, bearing tem
peratures rise, and fatigue failures occur in parts
such as gears, bolts, and bearings. Long con
tinued noise and vibration can affect people as
adversely as machines, causing human fatigue, im
paired judgment, and communications difficulties.
A tremendous variety of shock and vibration
problems plague industry today. Some are com
monplace; others strain the bonds of credulity. For
horizon-broadening purposes, a few samples —
representing different areas of application and in
terest—are presented.
■ Cold-header machines used by bolt manufac
turers were once lagged to concrete floors. They
often tore loose due to the severe shock forces.
Today, most machines are floated on soft mounts.
The mounts have sufficient flexibility and damp
ing capacity to dissipate the energy.
■ The same problem troubled the textile industry.
In times past, weaving looms worked well in multi
story wooden frame buildings. Shocks caused by
shuttle acceleration and deceleration were dis
sipated by motion of the looms on relatively soft
wooden floors. Then looms were installed in single
story concrete-floored buildings. Severe shocks
caused looms to fail quickly, and maintenance costs
soared. Here, as in the bolt-manufacturing indus
try, flexibility was restored by floating the looms
on vibration-isolation pads.
■ A police department found that daytime lie-de
tector tests could not be made anywhere in its
headquarters building because there was too much
noise and vibration from activities in other parts
of the building. Accordingly, such tests are per
formed at night, when the rest of the building is
I relatively quiet.
■ Office buildings today use lighter construction
which, unfortunately, has less structural damping
than older buildings. Simultaneously, more power
ful blowers, pumps, compressors, and other ma
chines are being installed, often on roofs of build
ings. The upper floors of many new buildings are
consequently unrentable, due to high levels of
vibration and sound.
May 29, 1969 117
