Description of BS ISO 8297:1994+A1:2021 2021

1.1 General

This International Standard specifies an engineering method (grade 2, as defined in ISO 2204) for determining 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 unspecified number of individual sources) having their main dimensions in the horizontal plane, and which radiate

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.

1.2 Type and size of noise source

The method is applicable to industrial areas where most of the equipment operates outdoors, not enclosed 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 continuous operations, such as drag lines or cable conveyors, 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 measuring 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, , between the measurement contour and the boundary of the plant, in relation to the square root of the plant area, S_p, and is given in table 1.

Table 1

Uncertainty inherent in the method

Value of	Uncertainty1 dB
0,05
0,1	± 2,5
0,2
0,5

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 different measurement positions, owing to the inhomogeneous distribution of sound sources within the plant. They do not include uncertainties due to variations 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.

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