<p>A resonator (3) is connected with an intake air pipe (8) and forms a resonant chamber (30) therein. The resonator (3) includes a diaphragm (4), which is generally planar and is disposed between an air passage (20) of the intake air pipe (8) and the resonant chamber (30). The diaphragm (4) forms multiple oscillation sections (40-42,45-51), which have different natural frequencies, respectively.
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