An adaptive expansion technique is introduced to the implement fast multipole method(FMM) for
acoustics problems at low frequencies in this work.This technique determines the number of expansion
terms in multipole to local(M2L) translations according to the distance between the two interaction boxes.As a consequence,the computational efficiency of the fast multipole method is improved significantly.Inaddition,the numerica examples demonstrate the adaptive algorithm is valid for the hyper-singular boundary face method(HBFM) with FMM and the dual boundary face method(CHBFM) with FMM,although it is obtained by the convention alboundary face method(CBFM) with FMM.