Sonic boom A sonic boom is a shock-wave, or pressure disturbance, caused by the movement of the plane through the air, much like the wave produced by the bow of a ship as it moves through water: just as the bow wave is produced for the entire journey of the ship, so the sonic shockwave occurs throughout the duration of a supersonic flight. In subsonic flight, the plane pushes the air ahead of it out of the way as it moves. When a plane is traveling faster than the speed of sound (i.e. faster than air molecules normally travel) the air ahead of it is not pushed out of the way: the air remains still until the plane has approached to within half an inch, at which point the air is forced aside in a few millionths of a second. This creates extreme local compression and heating, and a shockwave spreads outwards in a cone. This pressure wave extends as much as 25 miles on either side of the flight path, and may be experienced as a loud sound, with accompanying vibration severe enough in close proximity to break windows and damage buildings. Development had begun before the effects of sonic boom tests had been conducted. During 1961 and 1962, 150 supersonic flights were made over St Louis, Missouri, in 1964,
flights were made over Oklahoma City for five months, and in 1965, there was further testing over Chicago, Milwaukee, and Pittsburgh and finally, in 1966 and 1967 at Edwards Air Force Base in California. Animals were found to react more to the observers than to the sonic booms. Residents submitted claims for hundreds of thousands of dollars in damages from sonic booms for broken windows, cracked plaster, tile and brick. In addition, routine exercises flown by supersonic US Air Force jets resulted in $3,800,000 in sonic boom damage claims in a three-month period in 1967. In July 1967, the UK
Ministry of Technology staged eleven supersonic test flights over the south of England using
Lightning fighters. The booms were to be measured by the RAF to relate them to the resulting public reaction.
The Guardian's opinion survey stated: "Nearly two thirds of the population of Bristol were frightened, startled or annoyed by the sonic booms to which they were subjected to last week." The Ministry received 12,000 complaints.
Airport noise claims Both Wiggs and the Anti-Concord Project claimed that the Concorde was louder than conventional aircraft on take-off and landing as a result of its
delta wing being optimized for high speeds so it needed to use more power than conventional aircraft. When measured in 1977, the British
Civil Aviation Authority (CAA) noted: On departure, the Concorde was generally a few PNdb noiser than the older long-range jets at the fixed monitoring points and noticeably noisier both closer to and further from the airport. At the arrival sites, Concorde was a few PNdb noisier than the older long range jets, except at 1.5 km from runway threshold, where it was on a par with the B 707. In the US, the Concorde noise was measured at DFW and Dulles airports: Based on the data given in Tables 11 and 12, it appears that the approach noise of the Concorde is somewhat higher than that for present day commercial aircraft. The takeoff noise is, for locations close the airport, considerably higher than present aircraft. Considerably higher, here, means more than an order of magnitude (10 db) louder. ==International opposition==