A modular Active Noise Control exhaust silencing system is provided including a housing defining an acoustic enclosure having an acoustic outlet port. A speaker is disposed within the acoustic enclosure and an amplifier is disposed within the housing and connected to the speaker. A microphone is associated...http://www.google.fr/patents/US6072880?utm_source=gb-gplus-shareBrevet US6072880 - Modular active silencer with port dish
