练习材料：
Lesson 7-1 Bats
ˈlɛsn 7-1 bæts
Not all sounds made by animals serve as language, and we have only to turn to that extraordinary discovery of echo-location in bats to see a case in which the voice plays a strictly utilitarian role.
To get a full appreciation of what this means we must turn first to some recent human inventions. Everyone knows that if he shouts in the vicinity of a wall or a mountainside, an echo will come back. The further off this solid obstruction, the longer time will elapse for the return of the echo. A sound made by tapping on the hull of a ship will be reflected from the sea bottom, and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated. So was born the echo-sounding apparatus, now in general use in ships.
nɒt ɔːl saʊndz meɪd baɪ ˈænɪməlz sɜːv æz ˈlæŋgwɪʤ, ænd wiː hæv ˈəʊnli tuː tɜːn tuː ðæt ɪksˈtrɔːdnri dɪsˈkʌvəri ɒv ˈɛkəʊ-ləʊˈkeɪʃən ɪn bæts tuː siː ə keɪs ɪn wɪʧ ðə vɔɪs pleɪz ə ˈstrɪktli ˌjuːtɪlɪˈteərɪən rəʊl.
tuː gɛt ə fʊl əˌpriːʃɪˈeɪʃ(ə)n ɒv wɒt ðɪs miːnz wiː mʌst tɜːn fɜːst tuː sʌm ˈriːsnt ˈhjuːmən ɪnˈvɛnʃənz. ˈɛvrɪwʌn nəʊz ðæt ɪf hiː ʃaʊts ɪn ðə vɪˈsɪnɪti ɒv ə wɔːl ɔːr ə ˈmaʊntɪnsaɪd, ən ˈɛkəʊ wɪl kʌm bæk. ðə ˈfɜːðər ɒf ðɪs ˈsɒlɪd əbˈstrʌkʃən, ðə ˈlɒŋgə taɪm wɪl ɪˈlæps fɔː ðə rɪˈtɜːn ɒv ði ˈɛkəʊ. ə saʊnd meɪd baɪ ˈtæpɪŋ ɒn ðə hʌl ɒv ə ʃɪp wɪl biː rɪˈflɛktɪd frɒm ðə siː ˈbɒtəm, ænd baɪ ˈmɛʒərɪŋ ðə taɪm ˈɪntəvəl bɪˈtwiːn ðə tæps ænd ðə rɪˈsiːt ɒv ði ˈɛkəʊz, ðə dɛpθ ɒv ðə siː æt ðæt pɔɪnt kæn biː ˈkælkjʊleɪtɪd. səʊ wɒz bɔːn ði ˈɛkəʊ-ˈsaʊndɪŋ ˌæpəˈreɪtəs, naʊ ɪn ˈʤɛnərəl juːz ɪn ʃɪps.
动物发出的声音不都是用作语言交际。我们只要看一看蝙蝠回声定位这一极不寻常的发现，就可以探究一下声音在什么情况下有绝对的实用价值。
要透彻理解这句话的意义，我们应先回顾一下人类最近的几项发明。大家都知道，在墙壁或山腰附近发出的喊声，就会听到回声。固体障碍物越远。回声返回所用时间就越长。敲打船体所发了的声音会从海底传回来，测出回声间隔的时间，便可算出该处海洋的深度。这样就产生了目前各种船舶上普遍应用的回声探测仪。
任务配置：L0、L3、L4
知识笔记：
单词与短语
serve as作为...
utilitarian/ˌjuːtɪlɪˈteərɪən/pertaining to or consisting in utility.
To get a full appreciation of what this means 要透彻理解这句话的意义
in general use in sth在...普遍应用的...
练习感悟：最近复述时，感觉自己讲英语开始有节奏了，不像打机关枪一样，一会儿哑炮，一会儿又突突突。
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