For people, who are interested in sound, the field of sound technology is definitely making noise. In the past, sound engineers worked in the back rooms of recording studios, but many of today’s sound professionals are sharing their knowledge and experience with professionals in other fields to create new products based on the phenomenon we call sound.
Sound can be used as a weapon. Imagine that a police officer is chasing a thief. The thief tries to escape. And the officer can’t let him get away. He pulls out a special device, points it at the suspect, and switches it on. The thief drops to the ground. This new weapon is called a Long Range Acoustic Device（LRAD, 远程定向声波发射器）. It produces a deafening sound so painful that it temporarily disables a person. The noise from the LRAD is directed like a ray of light and travels only into the ears of that person, but it is not deadly.
For those who hunger for some peace and quiet, sound can now create silence. Let’s say you are at the airport, and the little boy on the seat next to you is humming（哼唱）a short commercial song. He hums it over and over again, and you are about to go crazy. Thanks to the Silence Machine, a British invention, you can get rid of the sound without upsetting the boy or his parents. One may wonder how the Silence Machine works. Well, it functions by analyzing the waves of the incoming sound and creating a second set of outgoing waves. The two sets of waves cancel each other out. Simply turn the machine on point it at the target, and your peace and quiet comes back.
Directed sound is a new technology that allows companies to use sound in much the same way spotlights（聚光灯）are used in the theater. A spotlight lights up only one section of a stage; similarly, a "spotsound" creates a circle of sound in one targeted area. This can be useful for businesses such as restaurants and stores because it offers a new way to attract customers. Restaurants can offer a choice of music along with the various food choices on the menu, allowing customers more control over the atmosphere in which they are dining. Directed sound is also beginning to appear in shopping centers and even at homes.
46. What could be inferred from Paragraph 2 about the effect of the LRAD?
AIt causes temporary hearing loss.
BIt slows down a running man.
CIt makes it easy to identify a suspect.
DIt keeps the suspect from hurting others.
47. The Silence Machine is a device specially designed to ________.
Asilence the people around you
Bremove the sound of commercials
Cblock the incoming sound waves
Dstop unwanted sound from affecting you
48. What feature do spotsounds and spotlights share?
AThey travel in circles.
BThey clear the atmosphere.
CThey can be transformed into energy.
DThey can be directed onto a specific area.
49. Directed sound can be used for ________.
Acreative designs of restaurant menus
Bideal sound effects on the theater stage
Cdifferent choices of music for businesses
Dstrict control over any suspicious customer
50. What does the passage focus on?
AHow professionals invented sound products.
BInventions in the field of sound technology.
CThe growing interest in the study of sound.
DHow sound engineers work in their studios.