首页
登录
职称英语
Blind people usually possess one advantage over other people who can see: t
Blind people usually possess one advantage over other people who can see: t
游客
2023-11-22
50
管理
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. [br] 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://tihaiku.com/zcyy/3210578.html
相关试题推荐
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Onceuponatime,peoplewholivedalonetendedtobethoseoneitherside
Peopleoftenfocusonthejobandincomepotentialthatcomeswithacolleg
Peopleoftenfocusonthejobandincomepotentialthatcomeswithacolleg
Peopleoftenfocusonthejobandincomepotentialthatcomeswithacolleg
随机试题
Youwillhearabusinesspresentationabout3simplesellingtactics.Asyoulis
Howdoyousendamessagetoasubmergedsubmarine,particularlyonecarryin
下列属于无机结合料稳定基层试验段养护7d后检测项目的有()。A.原材料的全
肺炎链球菌肺炎患者的并发症包括()A.胸膜炎 B.休克 C.心包炎 D
根据《建筑法》,按国务院有关规定批准开工报告的建筑工程,因故不能按期开工超过(
嗜铬细胞瘤的临床表现主要是由下列哪种物质作用于肾上腺素能受体所致A.多种肽类激素
()是个人事先约定偿还期的存款,其利率视期限长短而定。A.活期存款 B.定期存
头孢曲松钠与乳酸钠林格注射液直接混合,可导致()A.产生气体 B.溶液变
《民用建筑节能条例》规定,()组织竣工验收,应当对民用建筑是否符合民用建筑节能
乙方当事人的违约行为导致工程受到损失,甲方没有采取任何措施减损,导致损失扩大到5
最新回复
(
0
)