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
2013-11-10
82
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 per-son’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 unit 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 a-bout 25 ft. If 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 present, 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.
The attempt to help blind people to see with sound ________.
选项
A、was similar to the sound location system of the bats
B、led to a product that sent out sound waves of about 20,000 cycles per second
C、was experimented on a submarine
D、turned out to be a failure
答案
A
解析
文章第三段指出“The first steps to help blind people to see with sound are based on exactly the same principle.”也就是选A项的根据。B项不对,不是20,000 cycles per second;C、D两项没有根据。
转载请注明原文地址:https://kaotiyun.com/show/6vGK777K
0
专业英语四级
相关试题推荐
WheredomostpeoplethinkTwainwasborn?
Sincewearesocialbeings,thequalityofourlivesdependsinlargemeasureonourinterpersonalrelationships.One【C1】______o
XiaoWanghassolvedtheproblem______theTVwasoutoforder.
WriteonANSWERSHEETTWOanoteofabout50-60wordsbasedonthefollowingsituation:Youhavegotintroubleinyourcompu
Nowhereinnatureisaluminumfoundfree,owingtoitsalways______withotherelements,mostcommonlywithoxygen.
Rightatmomentalotofattention______childrenwholeaveschoolunabletoreadorwrite.
Itisfarbettertodowellabitofworkwhichiswell______alargefortune.
Ifinditeasiesttolookforwardbylookingbacktothe"GreatLaborMigration"of1948-55,seenatthetimeasamatterofbla
Thepolicehaddifficultyin______thefansfromrushingontothestagetotakephotoswiththesinger.
Someproductsrespondtoconsumers’needs;others,likeSony’sairboard,seektocreatethem.Likesendinge-mailsfromthepool
随机试题
下列情形中,成立共同犯罪的有()。
某企业常年生产需用的某部件以前一直从市场上采购。采购量在5000件以下时,单价为8元;达到或超过5000件时,单价为7元。如果追加投入12000元专属成本,就可以自行制造该部件,预计单位变动成本为5元。要求:用成本无差别点法为企业作出自制或外购
女患者,阴户肿痛,行动艰难,发热,口干纳少,大便秘结,小便黄少。舌红苔黄腻,脉沉数。妇科检查见右侧外阴红肿,触之较硬。首选:
APTT测定检测普通肝素抗凝治疗不恰当的是
3l岁女性,葡萄胎二次清宫后2月,阴道不规则流血持续存在,尿HCG(+)。如B超检查发现子宫肌层呈蜂窝样改变应考虑为
()是注射剂生产中使用量最多的一种溶剂。
根据我国现行《企业会计准则》,企业在资产负债表日或之前违反了长期借款协议,导致贷款人可随时要求清偿的债务,应当归类为()。
【2013年云南昭通.简答】影响小学生心理健康的因素是什么.
某市有关部门策划了一项“全市理想生活小区排列名次”的评选活动。方法足,选择10项指标,内容涉及小区硬件设施(住房质量、配套设施等)、环境卫生、绿化程度、治安状况、交通方便程度等。每项指标按实际质量或数量的高低,评以从1~10分之间的某一分值,然后求得这10
主板有许多分类方法,其中按芯片集的规格进行分类的是()。
最新回复
(
0
)