单项选择题
A.见图AB.见图BC.见图CD.见图D
The Home Centralization case described in the class is ...
判断题The Home Centralization case described in the class is Mattel’s Barbie dolls.
距某一线声源,处的声级为52dB,2r处的声级为49dB,在r至2r距离范围内该线声源可视作()。A.点声源B...
单项选择题距某一线声源,处的声级为52dB,2r处的声级为49dB,在r至2r距离范围内该线声源可视作()。