Sonic boom and the "rise time" of the shock which makes the boom seem louder. On most aircraft designs the characteristic distance is about , meaning that below this altitude the sonic boom will be "softer". However, the drag at this altitude or below makes supersonic travel particularly inefficient, which poses a serious problem. The pressure from sonic booms caused by aircraft often are a few pounds per square foot. A vehicle flying at greater altitude will generate lower pressures on the ground, because the shock wave reduces in intensity as it spreads out away from the vehicle, but the sonic booms
Sonic boom 1,300 recordings, some taken inside the shock wave by a chase plane, the SSBD demonstrated a reduction in boom by about one-third. Although one-third is not a huge reduction, it could have reduced Concorde's boom to an acceptable level; one below the FM = 1 limit stated above, for instance. As a follow-on to SSBD, in 2006 a NASA-Gulfstream Aerospace team tested the Quiet Spike on NASA-Dryden's F-15B aircraft 836. The Quiet Spike is a telescoping boom fitted to the nose of an aircraft specifically designed to weaken the strength of the shock waves forming on the nose of the