The　aim　of　this　work　is　to　design　and　implement　a　hybrid　passive/active　system　to　control　the　noise　radiated　by　a　generator　sets.　Passive　control　was　afforded　by　a　rectangular　enclosure.　Main　wall　panels　of　the　enclosure　were　made　of　sound　boarding.　Air　inlet　and　outlet　were　set　for　lowing　temperature　inside　the　enclosure.　The　multi-pass　dissipative　silencers　were　mounted　in　the　inlet　and　outlet　respectively,　two-stage　expansion　chamber　silencer　was　mounted　for　suppressing　exhaust　noise.　The　measured　insertion　loss　was　higher　than　25　dB.　Active　control　system　was　applied　in　order　to　suppress　low-frequency　noise　from　exhaust　opening　and　outlet　of　the　enclosure.　The　reference　signal　was　supplied　by　a　tachometer.　Hightemperature　loudspeakers　were　used　as　control　sources.　The　residual　signal　was　picked　up　by　microphones.　Experimental　results　showed　that　the　hybrid　methods　can　achieve　good　performance.　The　results　indicated　that　the　proposed　methods　can　efficiently　improve　the　noise　reduction　of　enclosure　in　generator　set.　©　(2006)　by　the　Katholieke　Universiteit　Leuven　Department　of　Mechanical　Engineering　All　rights　reserved.