Pressure waves at ground level were recorded from seventeen supersonic flights of B-58 Hustler bombers at Indian Springs, Nevada, in the summer of 1960. Sandia Laboratory microbarograph equipment, used for distant recording of atomic test blasts, was operated at four stations out to twenty miles normal to flight course. Recorded results are reported. A calculation has been derived for sonic boom ray propagation in the horizontally layered atmosphere. Computed ground-level sound patterns for Project Big Boom flights are shown. Several arguments are made concerning existing sonic boom prediction techniques. Big Boom flight paths were not known to adequate accuracy nor were a wide enough variety of flight parameters flown to allow empirical resolution of questioned factors in quantitative prediction. Maximum amplitude recordings from flights between 30,000 and 50,000 feet MSL at Mach numbers from 1.3 to 1.5, however, indicated that pressure waves from these flights were not large enough to break windows or cause other damage at ground level.