SPACE CENTER, Houston (AP) -- Recordings made by instruments sensitive to sound below the threshold of human hearing may help investigators build a timeline of any uncharacteristic movements made by the space shuttle Columbia minutes before it broke apart, scientists say. The instruments also captured an explosion high over Texas that one scientist said could have been Columbia's cabin rupturing. As parts of Columbia began to break off as the shuttle streaked across the West, the flight behavior of the normally streamlined spacecraft would have changed. Those changes would have generated distinctly different patterns of sound waves compared to previous shuttle flights. http://www.space.com/missionlaunches/sts107_sound_030216.html