A FIGHTER plane being flown at supersonic speeds over the Irish coast caused a huge bang, when it broke the sound barrier, sending North Wales homeowners scurrying for cover. Windows and homes shook in parts of Denbighshire and Conwy, and North Wales Police received countless calls from panicking residents who thought there had been an earthquake. The boom was caused by a Typhoon Eurofighter being tested over the sea after setting off from its base at BAe Systems headquarters at Warton, near Preston. But a spokeswoman stressed the weather had caused the bang and the plane had not ventured inland in contravention of aviation laws. She said: "We believe it was one of our aircraft that made the noise, but it was in a designated testing area about 20 miles out from the coast, basically on a routine test. "It happens all the time. However, the weather conditions meant the sound carried further than it would usually. "It's not out of the ordinary, but the wind would have meant that people might have felt or heard it this time." The loud bang was heard at around 5.50pm on Tuesday from as far afield as Rhyl in the east to Conwy in the west, and several miles inland. Glenn Ford at the British Geological Survey said the organisation had received numerous reports of the huge noise. He said: "We've got quite a lot of history of this type of event. "From the effects - doors and windows rattling, that kind of thing - small earthquakes and sonic booms can get confused. "The pressure waves continue until it releases its energy by hitting something, for example the coast. "It would have to have been fairly significant in UK terms to cause the disturbances that people are report-ing." Mr Ford said a similar effect could be caused by a small meteorite or satellite breaking up, both of which could travel at supersonic speeds. Last week people living in Llandrindod Wells in Powys reported a similar incident. Windows and homes shook in the town when the noise rang out at last Wednesday. Worried residents thought they were in the middle of a mini-earthquake and called the police and the RAF. Powys Council's headquarters was one of the buildings where the bang was heard and workers reported that windows shook. Caused by air-pressure waves A SONIC boom is an impulsive noise similar to thunder. It is caused by an object moving faster than sound - about 750mph at sea level. An aircraft travelling through the atmosphere continuously produces air-pressure waves, similar to the water waves caused by a ship's bow. When the aircraft exceeds the speed of sound, these pressure waves combine and form shock waves, which travel forward from the generation or "release" point.. As an aircraft flies at supersonic speeds, it is continually generating shock waves, dropping sonic boom along its flight path. | 
