43.1 Introduction

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In noise-reduction applications, the need for a reactive muffler usually arises when transporting gas

through a duct. For sound transmission through the duct to be minimized, an acoustic suppression

device must be incorporated into the duct system. For example, in internal-combustion engines, it is

required to reduce the intake and exhaust noise to acceptable levels. This may be accomplished by

inserting a muffler in the intake and exhaust ducting to attenuate the pressure pulsations before they

reach the environment.

A successful muffler design must satisfy at least the following three criteria: (1) muffler performance

as a function of frequency (the maximum permissible noise generated by the gas flow through the

muffler may have to be specified as well); (2) the maximum permissible average pressure drop through

the muffler at a given temperature and mass flow; (3) the maximum allowable volume and restrictions on

space utilization.

The customer may ask for a muffler with unrealistically high noise attenuation, virtually no

backpressure, and very small size. In addition, it is important to the customer that the muffler is

inexpensive and durable, and presents no maintenance problems. Needless to say, in practice, these

43-1

© 2005 by Taylor & Francis Group, LLC

criteria for muffler design are unrealistic, and have to be modified to practical levels. In this chapter, we

will present some of the analytical and empirical tools that are helpful in muffler design.

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