Absorptive Silencer Reactive Expansion Chamber

Cavity

Flow

Cavity

Reactive resonator. This type functions in approximately the same way as the reactive expansion chamber type.

Plenum chamber. This device allows the sound to enter a small opening in the chamber: that sound which has not been absorbed by the chamber's acoustical lining leaves by a second small opening, generally at the opposite end of the chamber.

Lined bend. Sound energy flowing down a passage is forced to turn a corner, the walls of which are lined with acoustical material. The sound energy is thus forced to impinge directly on a sound-absorbing surface as it reflects its way around the corner; each successive impingement takes sound energy from the traveling wave.

Diffuser. This device does not actually reduce noise. In effect, it prevents the generation of noise by disrupting highvelocity gas streams.

FIG. 6.7.8 Basic silencers.

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