You cast a 10ft spherical barrier at a point of your choosing, no sound can escape or enter this sphere. For example, if someone was to scream to another person from inside the barrier, then the other person would not hear it; nor could the person inside hear a response. The use of a bonus action will allow you to move the barrier up to 30ft, and also move it in such a way where you could get it to follow yours or another's movements. living creatures and objects can move freely inside and outside the barrier. The area of effect shimmers with magical aura very slightly, and can be seen with a investigation check against you spell level DC.
Casting this spell at 5th level or higher will increase the size of the barrier by 5ft with each level increase.