20181(B)A.B.C.D.2(C)A.B.C.D.3(C)A.B.C.D.4(D)A.B.C.D.5(D)A.B.C.D.6.(C)A.B.C.D.7500Hz15340m/s,(B)A.0.58mB.0.68mC.0.78mD.0.88m8(B)A.200Hz20000HzB.20Hz20000HzC.20Hz2000HzD.40Hz20000Hz9(D)A.B.C.D.10(D)A.B.C.D.1()()A.3dbB.10dbC.6dbD.8dbB.2()()A.8dbB.10dbC.6dbD.3dbD.3.(D)A.B.C.D.4.(C)A.B.C.D.5(B)A.B.C.D.6(A)A.B.C.D.7(B)A.B.C.D.8(A)A.B.C.D.9(B)A.B.