A silencer for silencing exhaust gases includes an acoustic resonator chamber that serves as a spark arrester to trap burning carbon particles and prevent them passing to the atmosphere. The silencer has an exhaust gas inlet and an exhaust gas outlet. Exhaust gases pass from the inlet to the outlet through a first passage and into a first chamber. The first chamber communicates with an acoustic resonator chamber by means of a connecting passage. The connecting passage is positioned adjacent the first passage so that sparks in the exhaust enter the acoustic resonator chamber where they are trapped. The silencer thus avoids the need for a separate spark arrester, as required by prior art silencers.