Standards Development

Scope

This document specifies methods for qualifying an environment that approximates to an acoustic free field near one or more reflecting planes. The goal of the qualification is to determine the environmental correction K_2, which is used to correct for reflected sound when determining the sound power level or sound energy level of a noise source from sound pressure levels measured on a surface enveloping the noise source (machinery or equipment) in such an environment. In addition, the environmental correction K_2 may be used as an input parameter for the determination of the local environmental correction K_3, which is used to determine the emission sound pressure level in an environment that approximates to an acoustic free field near one or more reflecting planes. In practice, the K_2 value determined will be a function of both the reflected sound from the test environment and the shape and size of the measurement surface used for the K_2 determination. For the purposes of this standard and the standards that refer to it, the differences between K_2 values determined with different measurement surfaces are assumed to be included in the stated measurement uncertainty for the test method. 

Purpose

The purpose is to specify methods for qualifying an environment that approximates to an acoustic free field near one or more reflecting planes.

For this proposal and its attached document in Annex A 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 proposed ISO 5114-1 " Acoustics — Determination of uncertainties associated with sound emission measures – Part 1: Sound power levels determined from sound pressure measurements". WG 28 recommends the parallel development of these three standardization projects to address comprehensive issues.