DNV 109 PDF

This Ecma Standard applies to information technology and telecommunications equipment.

This Ecma Standard specifies:

• the method for determining the mean A-weighted sound power level, L_WA,m for a batch of machines,

• the method for determining the mean A-weighted emission sound pressure level, L_pA,m for a batch of machines,

• the method for determining the statistical adder for verification, K_v for a batch of machines,

• the method for determining the statistical upper limit A-weighted sound power level, LWA,c for a batch of machines to be used for verification,

• acoustical and product information to be published electronically or in hard-copy format in technical documents or other product literature supplied to users by the manufacturer, and

• the method for verifying the noise emission values that are published or stated by the manufacturers and other product suppliers.

The uniform methods in this Ecma Standard use the noise emission data obtained in accordance with ECMA-74, and the procedures specified in ISO 4871 and ISO 7574-4.

The basic noise emission values to be declared or stated are the mean A-weighted sound power level, LWA,m and the mean A-weighted emission sound pressure level at the operator or bystander positions, L_pA,m. These are arithmetic mean values based upon measurements on a sample of machines in accordance with ECMA-74.

For verification purposes, an additional quantity is required to be stated or declared: the so-called statistical adder for verification. This is a factor that is added to the mean A-weighted sound power level and used in the verification section of this Standard to provide a consistent and predictable probability of acceptance for the batch of equipment.

The mean A-weighted sound power level for the batch of machines permits comparison of noise emissions between different products and permits predictions of installation or work-place noise immission levels, as described in ECMA TR/27.

Although the most useful quantity for calculating immission levels due to one or more sound sources is the A-weighted sound power level of the individual source(s), the A-weighted emission sound pressure level may also be useful in estimating the immission level in the immediate vicinity of an isolated piece of equipment.

To avoid confusion between sound power levels and emission sound pressure levels, the mean A-weighted sound power level, L_WA,m is stated in bels (B) and the A-weighted emission sound pressure level, LpA,m is stated in decibels (dB).