scope:

This Technical Specification specifies methods for thedetermination of insertion loss of outdoor noise barriers intendedto shield railway noise. It specifies detailed procedures for insitu measurement of barrier insertion loss including microphonepositions, source conditions and acoustic environments of themeasurement sites. This Technical Specification allows one tomeasure the insertion loss of a given noise barrier at a given siteincluding given meteorological conditions. It does not make itpossible to compare insertion loss values of an equivalent barrierat a different site. It can be used for comparing insertion lossvalues of different types of barriers at the same site under givenmeteorological conditions by the ?direct method?. This TechnicalSpecification gives a method for determining insertion loss: a)from the level difference before and after the installation ofnoise barriers (the ?direct method?); b) when the direct method isnot applicable, because a barrier has already been installed, usingan "indirect method" to estimate the sound pressure levels beforeinstallation of the barrier by measurement at another site whichhas been judged to be equivalent. For equivalent sites, a closematch is required in source characteristics, microphone locations,terrain profiles ground surface characteristics, surroundingartificial structures and meteorological conditions. This TechnicalSpecification prescribes principles for ensuring that sufficientlyequivalent conditions are maintained between ?before? and ?after?cases to permit certain, reliable and repeatable determination ofbarrier insertion loss. This Technical Specification does not coverthe determination of the intrinsic acoustic characteristics of thebarrier, for example the sound insulation index and the soundabsorption coefficient. The equivalent continuous A-weighted soundpressure level and one-third-octave band sound pressure level areused as noise descriptors. This Technical Specification can be usedfor routine determination of barrier performance or for engineeringor diagnostic evaluation. It can be used in situations where thebarrier is to be installed or has already been installed.