The speed with which sound waves move through a medium does depend on the properties of the medium.

Based on the figure, does S depend on the frequency of a sound wave of a given intensity?

A.Yes, because as frequency increases, S increases.

B.Yes, because as frequency increases, S remains constant.

C.No, because as frequency increases, S increases.

D.No, because as frequency increases, S remains

One of the mysteries of nature is animal communication. Creatures of the sea move through their liquid element without any hearable sound. Yet they are able to sense the silent passing or attack of others of their kind. This is because bodies moving in water create a pressure wave, something like a gust of wind produced by a passing automobile. A narrow sensor system running along each side of the shark, from eye to tail, receives and interprets these pressure waves. I have seen sharks appear swiftly, obviously drawn by the motion of a diver's hands, which had sent out strong waves.

One might think it impossible to distinguish odors in water. Yet sharks, surprisingly, are able to follow a scent across miles of ocean and arrive at its exact source. A diver who spears a fish and attaches its bloody body to his belt, and then goes on with the hunt, becomes a natural prey to the shark. I have seen sharks follow a scent exactly like the dogs of a hunting pack. It is no wonder that the Greeks gave them the name "hounds of the sea."

One of the most widely believed--and dangerous--legends about the shark is that he has poor eyesight. On the contrary, the shark is well equipped to see at a distance and to distinguish among forms. This fact was proved to me one day when I went into the water off the coast of Africa. I sighted a shark at some distance from me as I was floating at a very shallow depth. Since I was making no movement, the sound of bubbles from my diving apparatus would be confused with the light splashing of the water on a rock. I turned my eyes away for a few seconds, to study the design of a giant ray just beneath me. I am not sure now whether it was simple instinct or a feeling of movement, but I turned back abruptly toward the location of the shark. And, immediately, every muscle of my body tensed. He was no more than 30 feet away, launched toward me as hard and swift as a missile.

The sight of a shark coming at you head-on is strange. Obviously it is from this angle that he seems most frightening--the very symbol of evil, with the half-opened mouth and the three regularly spaced fins (鳍). When the shark had approached to within two feet of the rubber fins I had thrown at him as a gesture of self-defense, he turned suddenly and swam back toward the depths. There had been no sound, no scent. It appears certain that sight alone was responsible for this approach.

The best title for the passage is ______.

A．The Mysteries of Animal Communication

B．Something Unknown About Sharks

C．An Adventure

D．How Divers Discover Sharks Under the Sea

One of the mysteries of nature is animal communication. Creatures of the sea move through their liquid element without any hearable sound. Yet they are able to sense the silent passing or attack of others of their kind. This is because bodies moving in water create a pressure wave, something like a gust of wind produced by a passing automobile. A narrow sensor system running along each side of the shark, from eye to tail, receives and interprets these pressure waves. I have seen sharks appear swiftly, obviously drawn by the motion of a diver's hands, which had sent out strong waves.

One might think it impossible to distinguish odors in water. Yet sharks, surprisingly, are able to follow a scent across miles of ocean and arrive at its exact source. A diver who spears a fish and attaches its bloody body to his belt, and then goes on with the hunt, be comes a natural prey to the shark. I have seen sharks follow a scent exactly like the dogs of a hunting pack. It is no wonder th at the Greeks gave them the name "hounds of the sea."

One of the most widely believed — and dangerous — legends about the shark is that he has poor eyesight. On the contrary, the shark is well equipped to see at a distance and to dis tinguish among forms. This fact was proved to me one day when I went into the water off the coast of Africa. I sighted a shark at some distance from me as I was floating at a very shallow depth. Since I was making no movement, the sound of bubbles from my diving appa- ratus would be confused with the light splashing of the water on a rock. I turned my eyes away for a few seconds, to study the design of a giant ray just beneath me. I am not sure now whether it was simple instinct or a feeling of movement, but I turned back abruptly to ward the location of the shark. And, immediately, every muscle of my body tensed. He was no more than 30 feet away, launched toward me as hard and swift as a missile.

The sight of a shark coming at you head-on is strange. Obviously it is from this angle that he seems most frightening-the very symbol of evil, with the half-opened mouth and the three regularly spaced fins (鳍). When the shark had approached to within two feet of the rubber fins I had thrown at him as a gesture of self-defense, he turned suddenly and swam back toward the depths. There had been no sound, no scent. It appears certain that sight alone was responsible for this approach.

The best title for the passage is__________.

A．The Mysteries of Animal Communication

B．Something Unknown About Sharks

C．An Adventure

D．How Divers Discover Sharks Under the Sea

The speed ______ is 340 meters per second.

A．at which sound travels

B．with which sound travels

C．of which sound travels

D．for which sound travels

The speed ______ is 340 meters per second.

A．at which sound travels

B．with which sound travels

C．of which sound travels

D．for which sound travels

Although the distribution of recorded music went digital with the introduction of the compact disc in the early 1980s, technology has had a large impact on the way music is made and recorded as well. At the most basic level, the invention of MIDI (Musical Instrument Digital Interface), a language enabling computers and sound synthesizers to talk to each other, has given individual musicians powerful tools with which to make music.

"The MIDI interface enabled basement musicians to gain power which had been available only in ex- pensive recording studios," One expert observed. "It enables synthesis of sounds that have never existed before, and storage and subsequent simultaneous replay and mixing of multiple sound tracks. Using a moderately powerful desktop computer running a music composition program and a ' 500 synthesizer, any musically literate person can write -- and play! -- a string quartet in an afternoon."

Whereas many musicians use computers as a tool in composing or producing music, Tod Machover uses computers to design the instruments and environments that produce his music. As a professor of music and media at the MIT Media Lab, Machover has pioneered hyper - instruments: hybrids of computers and musical instruments that allow users to create sounds simply by raising their hands, pointing with a "virtual baton," or moving their entire body in a "sensor chair."

Similar work on a "virtual orchestra" is being done by Geoffrey Wright, head of the computer music, program at John Hopkins University's Peabody Conservatory of Music in Baltimore, Maryland. Wright uses conductors' batons that emit infrared light beams to generate data about the speed and direction of the batons, data that can then be translated by computers into instructions for a synthesizer to produce music.

In Machover' s best- known musical work, Brain Opera (1996), 125 people interact with each other and a group of hyper - instruments to produce sounds that can be blended into a musical performance. The final opera is assembled from these sound fragments, material contributed by people on the Web, and Machover's own music. Machover says he is motivated to give people "an active, directly participatory relationship with music."

More recently, Machover helped design the Meteorite Museum, a remarkable underground museum that opened in June 1998 in Essen, Germany. Visitors approach the museum through a glass atrium, open an enormous door, enter a cave, and then descend by ramps into various multimedia rooms. Machover com- posed the music and designed many of the interactions for these rooms. In the Transfiow Room, the undulating walls are covered with 100 rubber pads shaped like diamonds. "By hitting the pads you can make and shape a sound and images in the room. Brain Opera was an ensemble of imtividual instruments, while the Transfiow Room is a single instrument played by 40 people. The room blends the reactions and images of tile group."

Machover' s projects at MIT include Music Toys and Toys of Tomorrow, which are creating devices that he hopes will eventually make a Toy Symphony possible. Machover describes one of the toys as an embroidered ball the size of a small pumpkin with ridges on the outside and miniature speakers inside. "We' ve recently figured out how to send digital information through fabric or thread," he said. "So the basic idea is to squeeze the ball and where you squeeze and where you place your fingers will affect the sound produced. You can also change the pitch to high or low, or harmonize with other balls."

Computer music has a long way to go before it wins mass acceptance, however. Martin Goldsntitb, host of National Public Radio' s Performance Today, explains why: "I think that a reason a great moving piece of computer music hasn' t been written yet is that -- in this instance -- the technology stands between the creator and the receptor and prevents a real huma

A．makes it possible for anyone to write music

B．is only available in expensive recording studios.

C．requires high -end computers and programming skills.

D．provides cheap, powerful ways of making music