首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Blind people usually possess one advantage over other people who can see: their sense of hearing is far more acute. Sounds which
Blind people usually possess one advantage over other people who can see: their sense of hearing is far more acute. Sounds which
admin
2013-10-11
65
问题
Blind people usually possess one advantage over other people who can see: their sense of hearing is far more acute. Sounds which most others would miss can carry a great deal of information to a sightless person. For instance, teams of blind children can enjoy fast-moving games of soccer with a bell inside the ball and a new hand-held ultrasonic device to guide them. And that sound-location system could help to build up an even more complete sound picture of a blind person’s surroundings.
Bats, whose sight is poor, use a sound-location system to help them avoid obstacles in the dark. They send out pulses of sound waves, pitched at 50,000 cycles per second, far above the limits of the human ear, which can hear sounds up to frequencies of about 20,000 cycles per second. As the echoes bounce back off obstacles such as trees and walls, the bats are able to take appropriate action.
The first steps to help blind people to see with sound are based on exactly the same principle. The sound is emitted by an ultrasonic torch, shaped like a double-barreled version of a normal electric torch. It works in a similar Way to a sonar u nit on a warship or submarine.
The unit’s transmitter sends out pulses of ultrasonic waves at the same frequency as the bat, and the receiver picks up the returning echoes. Because these are still above the frequency at which the human ear can pick them up, the echoes are filtered through circuits which turn them into clearly audible ’ bleeps’ before passing them into headphones.
This means that a person holding the torch can point it ahead of him and ‘scan’the area for obstacles over a range of about 25 ft. ff there are no return echoes coming through the headphones, then there is nothing in the way.
If echoes do come back, then the closer the obstruction, the faster the succession of bleeps and the deeper the pitch of each bleep. With practice the torch could help a blind person to lead a more normal life -- without needing a constant companion to guide him. Experienced operators of the torch system claim they can distinguish grass from bushes, trees, pests and curbstones.
But before blind people can be helped to feel really independent, the system needs to be more streamlined. At pres ent, the experimental ultrasonic torch requires a shoulder bag to carry the batteries, cables for the power supplies and earphones, in addition to the torch itself. But miniaturization of electronic equipment is making such rapid progress that it should not be long before the whole set-up can be reproduced in a form small enough to fit into a pair of spectacles.
The transmitter and power supplies, with all the circuitry, would be packed into the bridge-piece above the nose. The sending and receiving sensors would be in the ’ lenses’. And the filtered bleeps would be passed on to the wearer through the earpieces, as with present-day hearing-aid spectacles.
This would mean that scanning one’s surroundings would become instinctive. The wearer would face in the direction he wanted to check, and lift or lower his head just as a sighted person would.
How do blind children play soccer?
选项
A、They listen to the sound of the ball bouncing.
B、They ask an adult to guide them.
C、They hold a bell in their hands.
D、They put a bell inside the ball.
答案
D
解析
文章第一段指出teams of blind children can enjoy fast-moving games of soccer with a bell inside the ball....因此是put a bell inside the ball。
转载请注明原文地址:https://kaotiyun.com/show/3EGK777K
0
专业英语四级
相关试题推荐
Tosurviveintheintensetradecompetitionbetweencountries,wemust______thequalitiesandvarietiesofproductswemaketo
Neverinmywildestdreams______thesepeoplearelivinginsuchpoorconditions.
Accordingtothereport,peoplefromwhichcountryworkinthelongesthoursaweek?
ThedisputebetweenNorthKoreaandtheUnitedStatesismainlyon______
Leaddeposits,whichaccumulatedinsoilandsnowduringthe1960’smid7O’s,wereprimarilytheresultofleadedgasolineemiss
Whydoesthewomangotoseeherprofessor?
Largecompaniesneedawaytoreachthesavingsofthepublicatlarge.Thesameproblem,onasmallerscale,facespractically
Forwhomisthelectureintended?
Itwaswhathemeantratherthanwhathesaid______annoyedme.
Maggietiptoedoverandtooktheclockawaybecauseshehatedtohearit_____whenshewastryingtogotosleep.
随机试题
求曲线y=x2与直线y=0,x=1所围成的平面图形绕x轴旋转一周所得旋转体的体积.
A.活疫苗B.死疫苗C.类毒素D.外毒素E.病原体的部分成分百日咳疫苗是
细菌性痢疾:血吸虫病:
关于糖尿病神经病变以下说法正确的是
有关大隐静脉的描述,下列哪项是恰当的
对于城镇街坊内部隐蔽的界址点及村庄内部界址点,其点位允许误差为()cm。
【背景资料】 某水库枢纽工程总库容1500万m3,工程内容包括大坝、溢洪道、放水洞等,大坝为黏土心墙土石坝,最大坝高为35m,坝顶构造如图1-1所示。 施工过程中发生如下事件。 事件1:为加强工程质量管理、落实质量责任,依据《关于贯彻质量发展纲要
因审计范围受到限制,不能获取充分、适当的审计证据,虽影响重大,但不至于出具否定意见的审计报告时,可以出具无法表示意见的审计报告。( )
下列选项中,有关PowerPoint。演示文稿的表述,正确的一项是()。
Babies’ResponseForsometimeinthepastithasbeenwidelyacceptedthatbabies,andothercreatureslearntodothingsb
最新回复
(
0
)