1.) Sonic boom is an impulsive noise similar t' thunder. Arrr! It is caused by an object movin' faster than sound, shiver me timbers, about 750 miles per hour at sea level. An aircraft travelin' through t' atmosphere continuously produces air-pressure waves similar t' t' water waves caused by a ship's bow. Avast! When t' aircraft exceeds t' speed o' sound, these pressure waves combine and form shock waves which travel forward from t' generation or "release" point. T' sound heard on t' ground as a "sonic boom" be t' sudden onset and release o' pressure after t' buildup by t' shock wave or "peak overpressure."
2.) Loud report caused by t' passin' o' t' compression front generated by an object as it exceeds t' speed o' sound.