Ergonomics - Atlas Copco

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microphones at a distance of 1 meter from
the machine. It can be argued that 1 meter
could be too far between the machine and the
operator’s ear. Comparisons between the av-
erage level and measurements made at the
operator’s ear for the same object are, how-
ever, very close due to the direction of the
noise scatter. Less noise is scattered in the
direction of the operator because the exhaust
air is directed away from the operator.
Calculation of dose
The declared noise level to which the operator
is exposed during the assumed average
time is recalculated to an 8-hour equivalent
level.
L eq(8) = 10log[1/8(10 L/10 T)]
L = noise level in real use, estimated with
the declared value.
T = assumed exposure time
Typical exposure times per day for different
machine types can be found in Table 3.10
The L eq(8) is then compared with a Threshold
Limit Value (TLV) for 8-hour exposure. In
our stressor comparison we assume 85 dB(A)
to give a score of 20.
Exposure time
We use the same average exposure time
as for vibration. The value can be found in
Table 3.13.
Score
40
30
20
10
0
Bibliography
ISO 3744, Determination of sound power levels of
noise sources using sound pressure. Engineering
methods in an essentially free field over a reflecting
plane.
ISO 15744, Hand-held non-electric power tools
– Noise measurement code – Engineering method
(grade 2).
Directive 2003/10/EC of the European Parliament
and of the Council of 6 February, 2003 on
the minimum health and safety requirements
regarding the exposure of workers to the risks
arising from physical agents (noise).
70 80 90 100
L eq(8) dB(A)
Fig. 3.23 The score for noise can be found using
L eq for an 8-hour working day as the input.