An Improved Active-Passive Hybrid Muffler

In the previous research, a kind of active-passive hybrid muffler has been developed for ventilation systems to reduce broadband noise. Its active part consists of an error microphone, a controller, a secondary loudspeaker and its power amplifier. A reference microphone is inside the passive part. The controller is outside the muffler and has little big size. In order to make it more compact, convenient and cheaper, an improved active-passive hybrid muffler is proposed in this work. The controller and power amplifier are integrated into one circuit board inside the muffler. Ordinary microphones are used as reference and error sensors. The muffler can identify the secondary-path transfer function automatically when the controlled system characteristics changes. Its passive and active-passive performances are validated by experiments.