Exodus 19:16

19:16 On the third day in the morning there was thunder and lightning and a dense cloud on the mountain, and the sound of a very loud horn; all the people who were in the camp trembled.

Exodus 20:18

20:18 All the people were seeing the thundering and the lightning, and heard the sound of the horn, and saw the mountain smoking – and when the people saw it they trembled with fear and kept their distance.

Exodus 28:35

28:35 The robe is to be on Aaron as he ministers, and his sound will be heard when he enters the Holy Place before the Lord and when he leaves, so that he does not die.