ACTIVE MUFFLER

PROBLEM TO BE SOLVED: To prevent the dew condensation on the connection route of an exhaust pipe with the sound instrument such as a speaker by the exhaust gas of high temperature and high humidity in the exhaust pipe, in an active muffler provided with the sound instrument acoustically connected through a connection route to a sound wave propagation route connected upstream to a noise source. SOLUTION: A cooling fan 15 for cooling an acoustic instrument is provided in a duct which is a connection route of an exhaust pipe 4 which is a sound wave propagation route with the acoustic instrument such as a speaker 13. This duct 5 is connected vertically and slantly downward for the exhaust pipe 4 and the water drop generated by a dew condensation is escaped from the acoustic instrument. Thereby, the stick of the water drop dew condensated in the duct 5 to the speaker 13 is prevented and the reliability and durability of the acoustic instrument can be improved.