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
2009-02-10
59
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.
Which of the following is NOT true about the ultrasonic torch?
选项
A、It enables the blind to live a more normal life.
B、It is mainly used to scan the area in front of the operator for obstacles.
C、Fast succession of bleeps indicates that the obstacle is near.
D、Its sound can warn other people of the blind man’s approach.
答案
D
解析
A项可从倒数第四段the torch could help a blind person to lead a more normal life得到根据;B项可从倒数第五段a person holding the torch can point it ahead of him and "scan"...得到证实;C项可从倒数第五段the closer the obstruction the faster the succession of bleeps得到证实;只有D项无出处。
转载请注明原文地址:https://kaotiyun.com/show/YJ6K777K
0
专业英语四级
相关试题推荐
EthicsinCompaniesI.TheimportanceofethicsA.【T1】______enablescompaniestoexploitthe【T1】______economicadvantages,w
EthicsinCompaniesI.TheimportanceofethicsA.【T1】______enablescompaniestoexploitthe【T1】______economicadvantages,w
EthicsinCompaniesI.TheimportanceofethicsA.【T1】______enablescompaniestoexploitthe【T1】______economicadvantages,w
A、Almostthewholeofhumanlife.B、Socialaspectsofhumanactivity.C、Socialrelationsofpeople.D、Howpeoplelearnfromothe
OscarWildesaidthatworkistherefugeofpeoplewhohavenothingbettertodo.Ifso,Americansarenowamongtheworld’ssa
Wearelivinginwhatwecallthesecondgreatchangeinthestateofman.Thefirstisthechangefrompre-civilizedtocivili
Unlikeanyothercreatureonthisplanet,humanscanlearnandunderstand,withouthavingexperienced.Theycanthinkthemselve
Unlikeanyothercreatureonthisplanet,humanscanlearnandunderstand,withouthavingexperienced.Theycanthinkthemselve
Unlikeanyothercreatureonthisplanet,humanscanlearnandunderstand,withouthavingexperienced.Theycanthinkthemselve
随机试题
JaneAustenisanEnglishwomannovelistofthe______century.
非凹陷性水肿见于
交互抑制也称为
中毒解救中禁用胆碱酯酶复活剂的是
根据《水利工程质量监督管理规定》,()有权提请有关部门奖励先进质量管理单位及个人。
在2001年至2010年期间,国家鼓励类产业的西部内资企业,其主营业务收入占企业总收入70%以上的,征收企业所得税的税率可适用( )。
教师之间的互评是发扬民主的一种评价方式,通常被称为(),主要通过交互诊断和课堂听课的形式进行。
给定资料1.近年来,随着经济社会的迅速发展,人民群众生活基本实现了小康。物质文化生活得到充分满足之后,人民群众的法制观念、权利意识普遍增强,公众愿望不断升级,社会诉求不断提高,但同时贫富差距也在拉大,处理各类社会矛盾的难度也更大。传统的社会管理体
[*]
设f(x)在[0,1]上有定义,且exf(x)与e-f(x)在[0,1]上单调增加.证明:f(x)在[0,1]上连续.
最新回复
(
0
)