Can You Hear This?
When something creates a sound wave in a room or anauditorium, listeners hear the sound wave directly from the source. They alsohear the reflections as the sound bounces off thewalls. floor, and ceiling. These are called the reflected wave or reverberant(反射)sound, which can be heard evenafter the sound is no longer coming from the source.
The reverberation time of an auditorium isdetermined by the volume or interior size of the auditorium. It is alsodetermined by how well or how poorly the walls, ceiling, floor, and contents ofthe room (including the people) absorb sound. There is no ideal reverberation time,because each use of an auditorium calls for different reverberation. Speechneeds to be understood clearly; therefore rooms used for talking must have ashort reverberation time. The full-sound performance of music such ad Wagneroperas or Mahler symphonies should have a long reverberation time. The light,rapid musical passages of Bach or Mozart need a reverberation time somewherebetween.
Acoustic problems often are caused by poorauditorium design. Smooth, curved reflecting surfaces create large reflections.Parallel (平行的)wallsreflect sound back and forth, creating a rapid, repetitive pulsing effect.Large pillars (柱)and comerscan 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 tochange the reverberation time of a room. For example, hanging large reflectors,called clouds, over the performers will allow some sound frequencies to reflectand others to pass to achieve a pleasing mixture of sound.
41 This passage is mainly about
A. Sound waves and their effects.
B. the types of music orchestras play.
C. walls of an auditorium.
D.the design of an auditorium.
42. Wagner operas and Mahler symphonieswith full-sound effect have
A. a short reverberation time.
B. an intermediate reverberation time.
C. no reverberation time.
D. along reverberation time.
43. This passage suggests that a goodauditorium should
A. get rid of all reflections.
B. not have absorbers.
C.achieve a pleasing mixture of sound
D. have smooth surfaces.
44. Large pillars and corners may
A. make sound rich and full.
B. be cures for sound problems.
C.be sources of sound problems.
D. function as effectively as clouds.
45. The word" acoustic" in thelast paragraph has something to do with