This International Standard specifies methods for the determination of insertion loss of outdoor noise barriers intended to shield various kinds of noise sources. It specifies detailed procedures for in-situ measurement of barrier insertion loss including microphone positions, source conditions and acoustic environments of the measurement sites.

This International Standard allows one to measure the insertion loss of a given noise barrier in a given site and including given meteorological conditions. It does not make it possible to compare insertion toss values of an equivalent barrier on a different site. It can be used for comparing insertion loss values of different types of barriers on a same site and under given meteorological conditions by the direct method.

This international Standard gives a method for determining insertion loss:

• from the level difference before and after the installation of noise barriers and when this is not possible because a barrier has already been installed,
• using an indirect method to estimate the sound pressure levels before installation of the barrier by measurement at another site which has been judged to be equivalent.

For equivalent sites, close match is required in source characteristics, microphone locations terrain profiles ground surface characteristics, surrounding artificial structures and meteorological conditions. This International Standard prescribes principles for ensuring that sufficiently equivalent conditions are maintained between “before” and “after” cases to permit certain, reliable and repeatable determination of barrier insertion loss.

This International Standard does not cover the determination of the intrinsic acoustic quantities of the barrier, for example the sound reduction index and the sound absorption coefficient. The equivalent continuous A-weighted sound pressure level, the A-weighted sound exposure level, the octave or one-third-octave band sound pressure level and/or maximum sound pressure level are used as noise descriptors.

This International Standard can be used for routine determination of barrier performance or for engineering or diagnostic evaluation. It can be used in situations where the barrier is to be installed or has already been installed.