BS EN ISO 3740:2019 pdf – Acoustics – Determination of sound power levels of noise sources – Guidelines for the use of basic standards.
1 Scope This document gives guidance for the use of a set of twelve basic International Standards (see Tables 1, 2 and 3) describing various methods for determining sound power levels from all types of machinery, equipment and products. It provides guidance on the selection of one or more of these standards, appropriate to any particular type of sound source, measurement environment and desired accuracy. The guidance given applies to airborne sound. It is for use in the preparation of noise test codes (see ISO 12001) and also in noise emission testing where no specific noise test code exists. Such standardized noise test codes can recommend the application of particular basic International Standard(s) and give detailed requirements on mounting and operating conditions for a particular family to which the machine under test belongs, in accordance with general principles given in the basic standards. This document is not intended to replace any of the details of, or add any additional requirements to, the individual test methods in the basic International Standards referenced. NOTE 1 Two quantities which complement each other can be used to describe the noise emission of machinery, equipment and products. One is the emission sound pressure level at a specified position and the other is the sound power level. The International Standards which describe the basic methods for determining emission sound pressure levels at work stations and at other specified positions are ISO 11200 to ISO 11205 (References  to ). NOTE 2 The sound energy level mentioned in ISO 3741 to ISO 3747 is not addressed in this document as it is not mentioned in any legal requirement. Its application is limited to very special cases of a single burst of sound energy or transient sound defined in ISO 12001. 2 Normative references There are no normative references in this document.
3.13 background noise level sound pressure level (3.5) measured when the source under test is not operating Note 1 to entry: It is expressed in decibels. 3.14 extraneous vibratory velocity level vibratory velocity level (3.10) caused by all sources other than the source under test Note 1 to entry: Extraneous vibratory velocity levels originate, for example, from coupled assemblies. [SOURCE: ISO/TS 7849-1:2009, 3.9] 3.15 background noise correction K 1 correction applied to the mean (energy average) of the time-averaged sound pressure levels (3.6) over all the microphone positions on the measurement surface, to account for the influence of background noise (3.12) Note 1 to entry: Background noise correction is expressed in decibels. Note 2 to entry: The background noise correction is frequency dependent; the correction of a frequency band is denoted K 1f , where f denotes the relevant center frequency, and that in the case of A-weighting is denoted K 1A . [SOURCE: ISO 3744:2010, 3.16] 3.16 environmental correction K 2 correction applied to the mean (energy average) of the time-averaged sound pressure levels (3.6) over all microphone positions on the measurement surface, to account for the influence of reflected or absorbed sound Note 1 to entry: Environmental correction is expressed in decibels. Note 2 to entry: The environmental correction is frequency dependent; the correction in the case of a frequency band is denoted K 2f , where f denotes the relevant mid-band frequency, and that in the case of A-weighting is denoted K 2A . Note 3 to entry: In general, the environmental correction depends on the area of the measurement surface and usually K 2 increases with S. [SOURCE: ISO 3744:2010, 3.17] 3.17 systematic deviation Δ sy deviation to account for a systematic difference between sound power levels (3.3) obtained using basic standards based on different physical rules
4 Sound power level 4.1 Basic information The sound power level characterizes the mean airborne acoustic energy flow from the source into the environment for a given mounting and operating condition and represents an intrinsic acoustic characteristic of the source that is independent of the environment in which it is installed. It is often denoted as an A-weighted sound power level, L WA , in dB. 4.2 Reasons for the determination of sound power levels Example situations where the A-weighted sound power level of a machine, equipment and product can be of interest are: — manufacturer noise emission declarations in the instructions and the sales literature according to regulations for machinery safety; — customer need for input to sound exposure prediction models which can support legal requirements for carrying out a noise exposure risk assessment; — customer need for comparison with the state of the art of noise emission, for comparing the data of competing machinery, equipment and products to support the “Buy Quiet” objective; — checking the noise emission level of machinery, equipment and products in specifications regardless of the environment in which they operate.