Hybrid approach to noise control of industrial exhaust systems

This study aims to present a procedure for optimal design of hybrid noise control systems for exhaust ducts from large fans and high radiated sound power, in an industrial environment. Reactive, resistive or hybrid silencers are considered as alternatives with the possibility of adding a supplementary active noise control system to mitigate remaining noise of multiple low frequencies, which are difficult to be attenuated by passive means. Algorithms are proposed for the implementation of optimal hybrid passive/active design and the main theoretical and practical fundamentals involved are showed. Two effective solutions for a real industrial exhaust system are presented as examples of applications of hybrid optimal design procedure proposed. The first one uses of Helmholtz resonators (to attenuate lower frequencies) and resistive silencer parallel lamellae (to lower the midrange and high frequencies). The second one adopts resistive silencer of parallel lamellae and a forward active noise control system. This is a hybrid approach that is not treated in this manner in the available literature, especially in the text books of applied acoustics engineering. (C) 2017 Elsevier Ltd. All rights reserved.