Category: (((—Acoustics Engineering—))))

10.9.1 Finite Element Analysis Young and Crocker [44–48] were the first to use finite element analysis in muffler design. So far in this chapter it has been assumed that the mufflers are axi‐symmetric in shape and acoustic filter theory [21, 22] provides a sufficient theoretical explanation for the behavior of muffler elements. This filter theory is…

10.8.1 Tail Pipe Radiation Early work on engine exhaust mufflers was hampered by a lack of knowledge of the reflection of waves at the end of the tail pipe. As Alfredson and Davies discuss [39], various assumptions have been made in the past about the magnitude and phase of the reflection (some researchers assumed the…

It will now be shown that for any linear passive muffler element that the TL is a property only of the muffler geometry (i.e. four‐terminal constants A, B, C, and D) and unaffected by connection of subsequent muffler elements or source or load impedances. On the other hand, it will be shown that the IL is affected by the…

10.6.1 Transmission Line Theory We will first make some simplifying assumptions: If plane waves are assumed to exist in a muffler element (see Figure 10.9) then the sound pressure p anywhere in the muffler element can be represented as the sum of right and left traveling waves p+ and p− respectively (10.2a) (10.2b) (10.3a) (10.3b) (10.3c) Note that p and V represent the magnitude (and phase)…

Although Quincke in the nineteenth century studied the interference of sound propagation through different length pipes, theory of real use in muffler design was not developed until the 1920s. This was probably partly because prior to this time it was difficult (if not impossible) to measure sound pressure quantitatively due to the lack of suitable…

Reactive mufflers can be subdivided into straight‐through and reverse‐flow types [4, 5]. Figure 10.2 shows some typical straight‐through types. These mufflers are usually comprised mainly of expansion chambers (chambers in which the area is suddenly increased then decreased) and concentric tube resonators (side‐branch Helmholtz resonators). Reverse‐flow types can be built in many different configurations. A typical reverse‐flow muffler…

The definitions of muffler performance in most common use will be given here [1, 5–8]. It should be noted, however, that some authors use different nomenclature and confusion can sometimes arise. The first three definitions are used frequently in work on mufflers for automobile engines and they are illustrated in Figure 10.1. It is of interest to…

Mufflers can be classified into two main types: reactive and dissipative. The design of reactive and dissipative mufflers is reviewed in a number of practical and theoretical books and book chapters [1–15]. Reactive mufflers are composed of one or more chambers and resonators of different volumes and shapes linked together by sections of pipe. They…

A muffler (also known as a silencer) is any section of pipe or duct which has been treated or profiled to reduce the propagation of sound from a source, while allowing the free flow of gas. The performance of a muffler is normally strongly dependent on frequency. A well‐designed muffler should have (i) an acoustical…