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.