Why don't we hear a sonic boom when a missile launches?

This is typically the case when a rocket is launched vertically - the missile is at first subsonic, and once it goes supersonic the shock wave is created but it propagates above our heads and upwards so that we don't hear it.

If however a supersonic rocket passes horizontally past you, or over you, then you can hear the sonic boom, as long as the missile is large enough and close enough.

Bullets are often supersonic but they do not create very large sonic booms when they go past you. People report a sort of buzzing or twanging sound as they pass nearby.

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David Kahana on Quora:

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