When something creates a sound wave in a room or an auditorium (礼堂) , listeners hear the sound wave directly from the source. They also hear the reflections as the sound bounces off the walls, floor, and ceiling. These are called the reflected wave or reverberant (反射的) sound, which can be heard even after the sound is no longer coming from the source.
The reverberation time of an auditorium is determined by the volume or interior size of the auditorium. It is also determined by how well or how poorly the walls, ceiling, floor, and contents of the room (including the people) absorb sound. There is no ideal reverberation time, because each use of an auditorium calls for different reverberation. Speech needs to be understood clearly; therefore rooms used for talking must have a short reverberation time. The full-sound performance of music such as Wagner operas or Mahler symphonies should have a long reverberation time. The light, rapid musical passages of Bach or Mozart need a reverberation time somewhere between.
Acoustic
problems often are caused by poor auditorium design. Smooth, curved (弯曲的) reflecting surfaces create large reflections. Parallel (平行的) walls reflect sound back and forth, creating a rapid, repetitive pulsing (有节奏的跳动) effect. Large pillars (柱) and comers can cause acoustic shadows as the sound waves try to pass around the object. Some of these problems can be solved by using absorbers and reflectors to change the reverberation time of a room. For example, hanging large reflections, called clouds, over the performers will allow some sound frequencies to reflect and others to pass to achieve a pleasing mixture of sound.
单选题
Wagner operas and Mahler symphonies sound with full-sound effect have ______.
【正确答案】
B
【答案解析】[解析] 事实细节题。由文章第二段中的“The full-sound performance of music such as Wagner operas or Mahler symphonies should have a long reverberation time. ”可知，瓦格纳的歌剧和马勒的交响曲听起来立体圆润是因为混响时间长，故选B。
单选题
This passage suggests that a good auditorium should ______.
【正确答案】
D
【答案解析】[解析] 推理判断题。第二段说到“each use of an auditorium calls for different reverberation”，说明礼堂需要不同的混响时间，第三段中的“Smooth, curved reflecting surfaces create large reflections. ”表明，建筑内部应该是光滑，有弧度的表面，这样混响的传声效果才好。综上，故选D。
单选题
Large pillars and comers may ______.
【正确答案】
C
【答案解析】[解析] 事实细节题。由文章最后一段中的“Large pillars and corners can cause acoustic shadows as the sound waves try to pass around the object...using absorbers and reflectors to change the reverberation time of a room. ”可知，建筑内的柱子和角落因声音需穿过障碍物可能会引起声影，接着又给出了解决办法，即在室内悬挂一些反射器，所以柱子和角落是声学问题的来源，故选C。
单选题
The word "acoustic" in the last paragraph has something to do with ______.