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, television stations always operate at the highest sound level allowed for reasons of efficiency. According to one NBC executive, no difference exists in the peak sound level of ads and programming. Given this information why do commercials sound so loud? The sensation of sound involves a variety of factors in addition to its speak level. Advertisers are skilful at creating the impression of loudness through their expert use of such factors. One major contributor to the perceived loudness of commercials is that mush less variation in sound level occurs during a commercial. In regular programming the intensity of sound varies over a large range. However, sound levels in commercials tend to stay at or near peak levels. Other “tricks of the trade” are also used. Because low-frequency sounds can mask higher frequency sounds, advertisers filter out any noises that may drown out the primary message. In addition, the human voice has more auditory ( 听觉的 ) impact in the middle frequency ranges. Advertisers electronically vary voice sounds so that they stay within such a frequency band. Another approach is to write the script so that lots of consonants ( 辅音 ) are used, because people are more aware of consonants than vowel ( 元音 ) sounds. Finally, advertisers try to begin commercials with sounds that are highly different from those of the programming within which the commercial is buried. Because people become adapted to the type of sounds coming from programming, a dramatic change in sound quality draws viewer a attention. For example, notice how many commercials begin with a cheerful song of some type. The attention-getting property of commercials can be seen by observing one-to two-year-old children who happen to be playing around a television set. They may totally ignore the programming. However, when a commercial comes on, their attention is immediately drawn to it because of its dramatic sound quality. 31. According to the passage, the maximum intensity of sound coming from commercials ________. A) does not exceed that of programs B) is greater than that of programs C) varies over a large range than that of programs D) is less than that of programs ( A ) 32. Commercials create the sensation of loudness because ________. 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 ( B ) 33. Many commercials begin with a cheerful song of some kind because ________. A) pop songs attract viewer attention B) it can increase their loudness C) advertisers want to make them sound different from regular programs D) advertisers want to merge music with commercials ( C ) 34. One of the reasons why commercials are able to attract viewer attention is that ________. A) the human voices in commercials have more auditory impact B) people like cheerful songs that change dramatically in sound quality C) high-frequency sounds are used to mask sounds that drown out the primary message D) they possess sound qualities that make the viewer feel that something unusual is happening ( D ) 35. In the passage, the author is trying to tell us ________. A) how TV ads vary vocal sounds to attract attention B) how the loudness of TV ads is overcome C) how advertisers control the sound properties of TV ads D) how the attention-getting properties of sounds are made use of in TV ads ( D )