Ergonomics - Atlas Copco

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value for 8 hours’ exposure to 87 dB(A) with
attenuation provided by ear protectors taken
into account. The directive also gives an
upper and a lower action value of 85 and 80
dB(A), respectively, without ear protectors.
When an action value is exceeded the
employer must take actions defined in the
directive. Dose meters that can be carried by
the operator during a full working day are
available for conducting these measurements.
Laboratory measurements
A standard was developed in the 1960’s for
measuring the noise levels of hand-held
power tools. It was the result of collabora-
tion between Pneurop (the European Com-
mittee of Manufacturers of Compressors,
Vacuum Pumps and Pneumatic Tools) and
CAGI (the Compressed Air and Gas Insti-
tute, in the USA).
The European Machine Directive states
that machine manufacturers are required to
declare noise emission levels from the tools.
If the sound pressure level is above 85 dB(A),
the sound power should also be stated.
The latter statement has led to some
confusion. Sound pressure levels and sound
power levels use the same unit, dB(A).
Sound power levels can be calculated from
a number of sound pressure readings over
a control surface. Pneurop and CAGI have
r = 1m
Fig. 3.21 Test surface containing five
microphone positions.
1m
produced two new standards incorporating
estimation of sound power. They are now re-
placed by the standard ISO 15744 published
on March 15, 2002.
At present, noise measurements are
performed in accordance with ISO 15744 for
pneumatic tools and EN 50144 or EN 60745
for electric tools.
Test procedure
The test object is held by an operator. The
distance from the geometrical center of the
machine to the microphones is 1 m. Four mi-
crophones are situated in a plane parallel to
the floor, and one microphone is placed 1 m
above the geometrical center of the machine.