Ergonomics - Atlas Copco

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Noise
Noise was the first environmental fac-
tor to be studied in the hand-held power
tool industry. Typical sources are the
common vane motor, escaping air, gears
and, in the case of very silent machines,
the vibrating housing itself. Sometimes
the process is the dominant source. This
has led to the development of machines
with new, more silent processes.
What is noise?
What we perceive as sound or noise (depending
on how we think of it) is a pressure
variation superimposed on the atmospheric
pressure. This pressure variation moves our
ear drums, resulting in a nerve signal to the
brain from the inner ear.
Pressure variations can be caused by
the loudspeakers in our stereo equipment,
by an oscillating plate, or by vibrations from
a machine housing. Other sources can be a
high velocity air flow, or a pulsating air flow
Acoustic testing using a test rig.
from a motor outlet. Noise can also be one
single pressure pulse from an impact.
How do we
measure noise?
A microphone converts the pressure varia-
tions into electrical signals that are amplified
and fed to a computer. Noise can be analysed
using an octave, 1/3 octave or 1/12 octave
analysis. It can also be analysed as a narrow