Ducted silencers: Transmission loss, transfer function method in ducts (NT ACOU 095)

Abstract

This method specifies the characterisation of duct silencers. It sets out requirements for determining the transmission loss of silencers, in frequency bands and without air flow. The measurement procedures are intended for laboratory measurements of silencers but may also be used for in situ measurements performed on silencers if the requirements of this method can be met. This method applies to silencers for ventilating and air conditioning systems which are usually connected to ducts or splitter absorbers mounted in ducts. The method does not apply to reactive silencers used for motor vehicles. NOTE 1. Exact information on the precision of the method cannot be given at this time. inter-laboratory tests are necessary for the determination of the reproducibility standard deviation OR of the method (relevant terms and methods are given in IS0 5725). Laboratory tests are however in good agreement with IS0 5725. The following estimates of the reproducibility standard deviation, OR, are therefore repeated from IS0 7235.