[提出问题]新年,学校要举行歌咏比赛,八年级2班到礼堂去试唱。礼堂里没有听众,也没使用扩音机。试唱结束,大家说效果很好,无论合唱还是独唱,歌声均十分响亮,坐在最后一排的听众也能听清楚。可是到了正式比赛,效果却差了一大截,独唱的声音很小,坐在后面的人根本听不到;大合唱虽然能听到,却比试唱时小多了。为什么声音变小了?被什么物体吸收了? [Ask questions] New Year, the school will hold a singing competition, eighth grade class to the auditorium to sing. There is no listener in the auditorium nor the megaphone. At the end of the audition, everyone said that the effect was very good. Both chorus and solo, the voices were very loud and the audience sitting in the last row could hear clearly. But to the official competition, the effect is a big difference, the solo voice is very small, people who sit behind can not hear; Although the chorus can hear, but smaller than the audition. Why is the sound smaller and absorbed by what?