One way of attenuating broad band noise that propagates through ducts or pipe systems is to use one or more reactive-type acoustic components, each of which is specifically designed for optimal performance at a particular frequency range. This paper uses the transfer matrix method for predicting the transmission loss (TL) of a system with resonators connected to the main duct and a side branch duct modified with a zero-mean-flow expansion chamber. The method is applied to different configurations, and the numerical predictions are compared with the results obtained using finite element methods. Our results indicate that broadband resonators and a side branch duct with an expansion chamber, fitted as a countermeasure for broadband noise, can offer significant benefits. © 2009 Institute of Noise Control Engineering.