Thunder

The sound of thunder is made by lightning. When lightning hits the earth's surface, there is a rapid expansion of air both around and within the bolt. The expansion of air produces a sonic shock wave which brings forth the sound we call thunder. The type of sound you hear from the bolt of lightning depends on the actual bolt and how far away you are from the lightning. Low and rumbling thunder is usually created from lightning that is father away, as apposed to crackling and sharp, loud cracks that are usually created from lightning that is closer.