Answers

2016-02-11T21:02:06+05:30
Sound is a mechanical wave and needs medium for propagation. Sound travels through solids, liquids and gases. Sounds does not travel in vacuum.
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2016-02-11T21:05:51+05:30
In contrast,electromagnetic waves require no medium, but can still travel through one.since a vacuum defined as lacking  a medium,then sound and correspondingly,mechanical waves,cannot propagate through a vacuum .this is why we cant hear  voices and sound in space.
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