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PTE听力考试高频真题——Summarise spoken text(2)

2017-08-14 10:10
摘要:下文是我们总结的听力高频考题,PTE听力薄弱的同学赶紧收藏啦!

  下文是我们总结的听力高频考题,PTE听力薄弱的同学赶紧收藏啦!

  1. 一种声音(翻译或者助听)设备的工作原理。

  (助听的,这个专业比较多,主要是说工作原理的-receptor,接受信息,振动人的耳朵,转化到什么什么语音:digital signal to actual sound之类的,这是对MIT students的一个remarkable device。)

  Abstract Most sounds of interest consist of complex, time-dependent admixtures of tones of diverse frequencies and variable amplitudes. To detect and process these signals, the ear employs a highly nonlinear, adaptive, real-time spectral analyzer: the cochlea. Sound excites vibration of the eardrum and the three miniscule bones of the middle ear, the last of which acts as a piston to initiate oscillatory pressure changes within the liquid-filled chambers of the cochlea. The basilar membrane, an elastic band spiraling along the cochlea between two of these chambers, responds to these pressures by conducting a largely independent traveling wave for each frequency component of the input. Because the basilar membrane is graded in mass and stiffness along its length, however, each traveling wave grows in magnitude and decreases in wavelength until it peaks at a specific, frequency-dependent position: low frequencies propagate to the cochlear apex, whereas high frequencies culminate at the base. The oscillations of the basilar membrane deflect hair bundles, the mechanically sensitive organelles of the ear's sensory receptors, the hair cells. As mechanically sensitive ion channels open and close, each hair cell responds with an electrical signal that is chemically transmitted to an afferent nerve fiber and thence into the brain. In addition to transducing mechanical inputs, hair cells amplify them by two means. Channel gating endows a hair bundle with negative stiffness, an instability that interacts with the motor protein myosin-1c to produce a mechanical amplifier and oscillator. Acting through the piezoelectric membrane protein prestin, electrical responses also cause outer hair cells to elongate and shorten, thus pumping energy into the basilar membrane's movements. The two forms of motility constitute an active process that amplifies mechanical inputs, sharpens frequency discrimination, and confers a compressive nonlinearity on responsiveness. These features arise because the active process operates near a Hopf bifurcation, the generic properties of which explain several key features of hearing. Moreover, when the gain of the active process rises sufficiently in ultraquiet circumstances, the system traverses the bifurcation and even a normal ear actually emits sound. The remarkable properties of hearing thus stem from the propagation of traveling waves on a nonlinear and excitable medium. 这段甚至比那段听力材料讲的还多,其实只要前半部分那个听到声音的过程就好了,尤其是前面关于介绍听力过程的那部分,差不多就一样了,声音什么震动鼓膜-传到耳蜗-大脑分析-做出反应

  Tapescript:Sound receptors. You’ve got sound receptors in your ear and they are beautiful. We’re not going to talk about them at any length, but there’s little flappy, these little spiky things going along in your ear and they can translate vibrational energy coming from your ear, hurting your eardrum, being translated into a vibration into the fluid in your ear into a physical motion of these little receptors there into an electrical motion, into an electrical signal that goes into your ear.So, all of that, all of that’s pretty impressive stuff. We’re not going to talk about the details of it, but I invite some of you who want to learn more about this, particularly MIT students I think find receptors really quite remarkable kinds of devices.

  Sample answer:The lecture is about how receptors work in the ear. When the sounds pierce into the eardrum, they can translate vibration from outside into a vibration into the fluid in the ear. Then the receptors turn the physical motion into an electrical motion. The electrical signals can then be analysed by the brain. The receptors are really remarkable kinds of devices.

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