A.0.6 B.0.8 C.1 D.1.2
A.≤0.04dB、≤0.1dB B.≤0.08dB、≤0.14dB C.≤0.64dB、≤0.12dB D.≤0.12dB、≤0.38dB
A.300-500 B.500-1000 C.1000-2000 D.2000以上