G D ：g a s t r o d u o d e n e c t o my , P D ：p a n c r e a t o d u o d e n e c t o my , P p P D ：p y l o r u s -p r e s e r v i n g P D, P R ：p a r t i a l r e s e c t i o n , n . d . ：n o t d e s c r i b e d

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W6 propose ANC ( ac もtve noise control )with IMC ( interna乳 model contro1 )in FB controL ． This IMC is known as a robust control design method especially fbr non − 1inear systems ． Noise is removed by activdy con もrolled secondary sound waves ． The perfbrmance ofFB − ANC can be predicted by investiga もillg もhe sensitivity fUnction． W ¢ examine realization of this control system by using simulation ． We can reduce the noise level remarkably over lower 貸 equency