NBN ISO 8297:2021

I .I General
This International Standard specifies an engineering
method (grade 2, as defined in IS0 2204) for deter-
mining the sound power levels of large multisource
industrial plants relevant to the evaluation of sound
pressure levels in the environment. These sound
power levels may be used in an appropriate prediction
model for such an evaluation.
The method is limited to large industrial plants with
multiple noise sources (a combination of an unspeci-
fied number of individual sources) having their main
dimensions in the horizontal plane, and which radiate
sound substantially uniformly in all horizontal di-
rections.
Unweighted sound pressure levels are measured in
octave bands.
The results obtained are expressed both in octave-
band sound power levels and, if required, in A-
weighted sound power levels.
I.2 Type and size of noise source
The method is applicable to industrial areas where
most of the equipment operates outdoors, not en- ’
closed by a building, e.g. petrochemical complexes,
factories, stone quarries, crushing plants and pithead
installations. The method is also applicable when
there are moving sources performing cyclic or con-
tinuous operations, such as drag lines or cable con-
veyors, provided that the measurements can be
related to at least one cycle of operation.
It is applicable to industrial plants in which the largest
horizontal dimension of the plant area lies between
16 m and approximately 320 m.
1.3 Types of noise
This International Standard applies to sources which
radiate broad-band noise, narrow-band noise, discrete
tones, repetitive impulsive noise and combinations of
such components. The procedure given is applicable
to steady noise and to non-steady noise provided that
it is statistically stationary. It is not suitable for meas-
uring isolated bursts of sound energy. The method is
best suited for broad-band steady noise.
1.4 Measurement uncertainty
The uncertainty inherent in the method due to the
layout of the plant depends mainly on the average
distance, d, between the measurement contour and
the boundary of the plant, in relation to the square
root of the plant area, S,, and is given in table 1.

IS0 8297:1994(E) 0 IS0
Table 1 - Uncertainty inherent in the method
Value of diJso
Uncertaintyl)
dB
I ~fr z5
+2,0
-2,5
+I,5
-2,0
1) Expressed as a 95 % confidence interval for one
determination.
These uncertainties arise from spatial variations in the
sound pressure levels (averaged over time) at the dif-
ferent measurement positions, owing to the inhom-
ogeneous distribution of sound sources within the
plant. They do not include uncertainties due to vari-
ations in the noise emissions of the sources over a
period of time.
NOTE 1 In cases where background noise corrections in
accordance with 9.5.4 cannot be applied, the uncertainties
may be greater than those given in table 1.
2