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举一反三
【单选题】Every year television stations receive hundreds of complaints about the loudness of advertisements. However, federal rules forbid the practice of making ads louder than the programming. In addition, t...
A.
TV stations always operate at the highest sound levels
B.
their sound levels are kept around peak levels
C.
their sound levels are kept in the middle frequency ranges
D.
unlike regular programs their intensity of sound varies over a wide range
【多选题】以下是纯音的是()。
A.
人的说话声
B.
录音师使用的调音台上的纯音发生器发出的声音
C.
频谱只有单一一条谱线的声音
D.
汽车的引擎声
E.
舞台上乐手使用唯一一种乐器发出的声音