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
90
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
Today,California’spublicschoolsareadisaster.【C1】______bydysfunctionanddisrepair,theyrankatthebottomofthecountry
WriteonANSWERSHEETTWOacompositionofabout200wordsonthefollowingtopic:MyViewonTrav
Howmanypeoplelosttheirlivesintheepidemic?
Leaddeposits,whichaccumulatedinsoilandsnowduringthe1960’smid7O’s,wereprimarilytheresultofleadedgasolineemiss
Whatarethepossiblerelationshipbetweenthemanandthewoman?
WriteonANSWERSHEETONEacompositionofabout150wordsonthefollowingtopic:TheAdvanta
WhichofthefollowinggiftsmaybeonanormalChristmaswishlist?
ItwasreportedthataunifiedstyleofuniformissettobewornbyallstudentsinJiangningDistrictofNanjing,whichisreg
TheWhitebrothers______thedesignofthefirstsuccessfulmotor-poweredplane.
StrikesanddemonstrationsinGermany,BritainandFrancehelpedtomaketheshorterworkingweekaunionpriority.Employersga
随机试题
特殊管理药品的应用A.转售B.涂改C.滥用D.账物相符E.在医院出售医疗单位购买的精神药品只准在本单位使用,不得
政府应是最讲诚实信用的正式组织机构,政府机关的行为应有连续性和(),不能朝秦暮楚、随意改变。
DRAM存储器的中文含义是()。
个人银行结算账户仅限于办理现金存取业务,不得办理转账结算。 ( )
汉译英:“发货港”,正确的翻译为( )。
某公司2009年1月1日发行在外普通股30000万股,7月1日以2008年12月31日总股本30000万股为基数每10股送2股;11月1日回购普通股2400万股,以备将来奖励管理层之用。若该公司2009年度净利润29904万元,则其2009年度基本每股收益
量子计算机是一类遵循量子力学规律进行高速数学和逻辑运算、存储及处理量子信息的物理装置,运行的是量子算法,处理速度大大超过传统计算机。量子计算机具有超高运算速度的原理在于()。
技术革新
以下关于网络操作系统的描述中,哪种说法是错误的?()
以下选项中表示一个合法的常量是(说明:符号□表示空格)
最新回复
(
0
)