Question

What happens when sound is produced in vacuum?

Answer 1

sound is produced but it is not reached to our ears..due to there is no medium to travel

Answer 2

That is correct, sound needs a media to propagate. 
Sound can not propagate in a vacuum. 
Sound waves, unlike light, are essentially compression waves and the 
sound in order to move from one place to other needs molecules to 
compress and decompress against, hence the wave is transmitted. In a 
vacuum, there are no molecules. Hence no sound.