声波传递需要介质，空气，水，岩石都行。
They need something to move through, like air, water, or rock.
辐射是一种既不需要介质也不需要与辐射体接触而进行的能量传输形式。
Radiation is a form of energy transfer that does not require a supporting medium nor contract with radiating body.
这可能是创建系统备份的一种灵活方法，而且不需要物理介质。
This can be a flexible way to make system backups without the need for physical media.
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