河北省昌黎县2014高考英语学生自选训练（4）及答案
[科普知识型阅读理解(一)]
A blind baby is doubly handicapped. Not only is it unable to see, but because it cannot receive the visual stimulus(刺激)from its environment that a sighted child does, it is likely to be slow in intellectual development. Now the tenmonthold son of Dr and Mrs Dennis Daughters is the subject of an unusual psychological experiment designed to prevent a lag(滞后)in the learning process. With the aid of a sonartype electronic that he wears on his head, infant(婴儿) Dennis is learning to identify the people and objects in the world around him by means of echoes(回声)．
The device is an improvement of the “Sonicguide”， an instrument produced by Telesensory Systems, Inc., of Palo Alto, Calif, and used by blind adults in addition to a sane or guide dog. As adapted for Dennis, it consists of a batterypowered system about the size of a half dollar that is on a headgear. A transmitter sends out an ultrasonic(超声的) pulse that creates an 80 degree cone of sound at 6 feet. Echoes from objects within the cone are perceived (felt) as sounds that vary in pitch(音调) and volume(音量) with the size and distance of the object.
The closer an object is, the lower the pitch, and the larger the object, the louder the signal. Hard surfaces produce a sharp ping, while soft ones send back signals with a slightly fuzzy quality. An object slightly to the right
