2014英语四级听力练习:慢速英语(9)_大学英语听力

2014英语四级听力练习:慢速英语(9)

　　Between 2000 and , the CTBTO recorded 26 powerful explosions of large meteorites entering the atmosphere.

　　The B612 Foundation also studies meteorite impacts. This group estimates at least four of those 26 explosions were stronger than the nuclear bomb that destroyed Hiroshima.

　　In addition to loud noise, explosions create low frequency infrasound. Sound waves can travel very long distances at such low frequencies. But human beings are unable to hear them.

　　CTBTO stations as far away as the Antarctica recorded the explosion of the Chelyabinsk meteorite.

　　Mr. Mialle says listening stations operate anywhere from four to 15 high-technology sensors. He says that the sensors work like large microphones.

　　They are called micro barometer because they measure micro fluctuations of the atmosphere. Its like a large microphone except theres no membrane.

　　He adds that some of the explosions are hard to identify immediately after they are recorded.

　　For instance, the first time we had this, what was later called the Super Bolide of North Pacific, in the first few weeks all that was known was a large event in the middle of the Pacific. But we didnt know what it was.

　　The commission keeps contact with other agencies, such as the American space agency, that follow meteorites. Space agency officials later confirmed that the mysterious explosion was caused by a meteorite.