scope:

Scope and field of application

This International Standard applies to computer and business equipment.

This International Standard specifies

- the method for determining the declared noise emission values;

- acoustical and product information to be given in technical documents supplied to users by the manufacturer;

- the method for verifying the declared noise emission values given by the manufacturers.

The uniform methods in this International Standard use the noise data obtained in accordance with ISO 7779 and the procedures specified in ISO 4871 and ISO 7574.

The basic declared noise emission values are the declared A-weighted sound power level, L_WAd (a statistical maximum value corresponding to L_c in IS0 75741, and the declared A-weighted sound pressure level, L_pAm (a mean value), at the operator or bystander positions.

The declared A-weighted sound power level, L_WAd, permits comparison of noise emissions between different products and permits predictions of installation or workplace noise exposure levels ¹⁾.

Although the most useful quantity for calculating exposure levels due to one or more sound sources is usually the declared A-weighted sound power level of the individual source(s), the declared A-weighted sound pressure level, L_pAm, may be used to estimate the exposure level in the immediate vicinity of an isolated piece of equipment.

To avoid confusion between sound power levels and sound pressure levels, the A-weighted sound power level is declared in bels and the A-weighted sound pressure level is declared in decibels.

¹⁾ If the declared A-weighted sound power level, L_WAd, in bels (B), is to be used for the determination of installation noise levels, or for comparison with the declared A-weighted sound power levels in decibels (dB) for machines other than computer and business equipment, the value of L_WAd in bels is multiplied by ten to obtain its value in decibels, using the identity 1 B = 10 dB.