Muffling Devices

In this chapter, the reader is introduced to:

noise reduction, NR, and transmission loss, TL, of muffling devices;

diffusers as muffling devices;

classification of muffling devices as reactive and dissipative;

acoustic impedance for analysis of reactive mufflers;

acoustic impedance of orifices and expansion chambers;

analysis of several reactive muffler types;

pressure loss calculations for reactive and dissipative mufflers;

lined duct mufflers and splitter mufflers as dissipative mufflers;

design and analysis of lined ducts;

duct break-out noise transmission calculations;

lined plenum attenuators;

water injection for noise control of exhausts; and

directivity of exhaust stacks.