BGS have received numerous reports from residents in Cornwall who reported an event at approximately 11:40 UTC (12:40 BST). Reports described "a loud rumbling was felt/heard", "loud noise and shaking which was felt and heard by others", "crockery rattled", "shutter door in factory rattled significantly and "roof joints creaked" The extent of the effects of the sonic boom were felt over a distance of approximately 40 km, stretching from Padstow to Tavistock.
Data from the BGS seismic networks in the region were examined and a signal consistent with a possible sonic origin was recorded at 11:38 & 11:39 UTC on two seismic stations in the area. The reports received are also consistent with historical observations received for previous events with a sonic origin.
RAF flying complaints have been contacted but were unable to confirm (at this time) if aircraft were operational at the time.
A sonic boom is the sound associated with the shock waves created when an object, such as an aircraft, breaks the sound barrier. An aircraft travelling slower than the speed of sound (~760 mph) creates a series of audible pressure waves that spread out in front and behind it. These waves travel at the speed of sound. As the speed of the aircraft increases these waves get closer together and at the speed of sound they merge into a single shock wave that starts at the nose and ends at the tail of the aircraft.
The boom is created by the sudden increase in pressure at the nose and also as the pressure returns to normal at the tail as the aircraft passes. This can lead to a distinctive "double boom". The shock wave or boom continues to be generated for as long as the aircraft is supersonic, which is why they are typically observed along a long strip along the flight path of the aircraft.