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 drop calculations for reactive mufflers;

  • lined duct silencers as dissipative mufflers;

  • duct break-out noise transmission calculations;

  • lined plenum attenuators; and

  • directivity of exhaust stacks.

8.1 Introduction

Muffling devices are commonly used to reduce noise associated with internal combustion engine exhausts, high pressure gas ...

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