Sonic boom:

A sonic boom is produced when an object travels through the air faster than the speed of sound. When an aircraft travels in air it creates a series of pressure waves which are in front and behind the aircraft. The pressure waves travel at the speed of sound. As the speed of aircraft increases, these waves are forced together and are compressed. These words merge to form a single shock wave that travels at the speed of sound.

The shock wave starts at the nose of the aircraft and ends at the tail. Pressure rises at the nose which decreases to a negative pressure at the tail which is followed by returning to normal pressure after the passing of the object. Boom is experienced when there is a sudden change in pressure. There is a distinctive double boom for a supersonic aircraft. When there is initial pressure-rise and it reaches to the observer and another when pressure comes back to normal.

Sonic boom is a thunder-like noise when aircraft flies overhead faster than the speed of sound.

Mach cone:

When aircraft smoothly flies at a speed greater than Mach 1, then shock waves and area bounded by the sides of these shock wave forms a Mach cone. 

Mach cone