If an object's speed exceeds the speed of sound, it is said to be travelling at:

Supersonic speed is the speed of an object that exceeds the speed of sound, which is approximately 768 miles per hour at sea level.

If  an object's speed exceeds the speed of sound, it is said to be travelling at supersonic speed. Bullets, jet aircraft, and other objects frequently travel at supersonic speeds. When a sound-producing source moves faster than the speed of sound, shock waves are created in the air.