Standards Development

Scope

This document gives guidance on the determination of (measurement) uncertainties of sound power levels determined according to ISO 3741, ISO 3743-1, ISO 3743-2, ISO 3744, ISO 3745, ISO 3746 and ISO 3747.

Purpose

An assessment of uncertainties that is comprehensible and close to reality is indispensable for reporting and applying measured sound power levels. Uncertainties should preferably be determined following the principles of ISO/IEC Guide 98-3. This Guide specifies a detailed procedure for the uncertainty evaluation that is based upon a complete mathematical model of the measurement procedure. At the current knowledge, it is impossible to formulate these models for sound power level measurements. To come to uncertainties all the same, the concept of reproducibility is additionally described in this document. This concept offers the possibility to state the uncertainty of a method and of measurements carried out according to the method, based on the results of inter-laboratory measurements.

For this proposal and its attached document in Annex A the ISO/TC 43/SC 1/WG 28 "Basic machinery noise emission standards" considered the feedback from its expert members on several internal preliminary working drafts. This included also the discussion of the proposed revision of ISO 3744:2010 "Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Engineering methods for an essentially free field over a reflecting plane" and development of the proposed NWIP for ISO 26101-2 "Acoustics – Test methods for the qualification of the acoustic environment – Part 2: Determination of the environmental correction". WG 28 recommends the parallel development of these three standardization projects to address comprehensive issues.