A Helmholtz resonator includes a chamber at least partially defining a
cavity. The chamber has a neck which defines a passage that is in fluid
communication with the cavity. The chamber and the neck produce a passive
response to a sound wave produced by the internal combustion engine. The
sound wave negatively effects engine performance. An active resonator is
disposed within the chamber. The active resonator produces a forced
response for supplementing the passive response and increasing the band
width of the noise attenuating pressure wave. The Helmholtz resonator is
in fluid communication with a portion of an air induction system that
defines a passageway that carries the sound wave. A driver is connected to
the active resonator, which is preferably a loud speaker, to drive the
loud speaker and produce the forced response. The driver preferably
utilizes a signal source, such as an engine speed signal, to synchronize
the forced response with the engine speed. A phase compensator
synchronizes the forced response with the sound wave, and an amplifier
amplifies the signal to drive the loud speaker.
