托福听力考试机经2018年

　　托福听力考试机经2018年!同学们在备考托福考试的前夕，可以利用机经来进行备考，这样能够减少我们的复习任务，并且能够有重点的来进行复习。今天小编在这里为大家整理到的是2018年的托福听力考试机经，供大家进行参考。

　　[L2-3]Listen to part of a lecture in a meteorology class.

　　Professor. OK. It’s important to measure a hurricane’s intensity before it reaches land because it can help save lives and avoid the enormous costs of an unnecessary evacuation. But the factors leading to a hurricane’s intensity like wind speed is very tricky to measure ‘cause they’re changing constantly. So can anyone tell me how we get information about the intensity of a hurricane that’s on the way? Jennifer?

　　Jennifer. Well, don’t we…like....fly planes into it?

　　Professor: Right. Planes that monitor hurricanes fly through the eye of a hurricane to measure the speed of the storm’s wind. But it’s very expensive and brings a lot of risks.

　　Jennifer: I understand the point about it being risky for the pilots with the high winds and lightning and everything. But um..^ how can it be so expensive?

　　Professor. Well. You see, hurricane-monitoring planes are built to withstand strong winds. And theyJre usually loaded with a lot of sophisticated equipment that will measure wind speed and other things. One plane costs about 100 million dollars and its single flight costs like... 50 thousand dollars. Plus, it can take as many as 10 flights to monitor a hurricane as it approaches land. From the readings of these direct measurements of hurricane force, we can determine whether to evacuate the area^ But that’s an expensive approach. I mean, we can’t simply fly planes into every hurricane and cyclone.

　　Now a couple of researchers think there may be a better way to measure a hurricane’s intensity... uh…a much more cost-effective way. It has almost no risks and requires much lower tech eauicment so this method is very promising. It’s a microphone…an underwater hydrophone. OK，so, how it works is…um…it receives acoustic waves underwater?By measuring

　　the noise of a hurricane underwater, we can predict the speed of hurricane winds with an amazing precision. Yes, John?

　　John: But how can we hear winds blowing over the water if the microphone, the hydrophone is underwater?

　　Professor. Well, hurricanes don’t just blow over the water leaving it untouched, do they?钏 John: Oh yeah. The water gets churned up.^

　　Professor. Hurricanes chum up the waves like crazy. The roiling action of the wind actually turns the water into a bubble-filled froth. And all this action creates a unique rumbling sound under the water whose volume is a good indicator of the intensity of the storm …uh …the speed of the hurricane winds. Uh... hydrophones can be deployed hundreds of meters below the surface ahead of the hurricane^ path while conditions are still safe. Also, the total cost for such a deployment would be a small fraction of the cost of even a single flight into the storms

　　Jennifer. I wonder how they figured this out. I mean, how would it occur to anyone to put a microphone under water to measure the speed of the hurricane winds?

　　Professor: Well, this actually brings us back to something Fve talked about in class before. ItJs the... ah…value of combining scientific disciplines to deal with complex meteorological problems. In this case, the idea came to light when two researchers from different fields met a few years ago. One was Nicholas Makris, an expert of underwater acoustics and the other was Kerry Emmanuel，a hurricane expert. So", uh…well", the research was triggered by their conversations Emmanuel asked Makris, t4Is it possible that underwater noise could be analyzed to determine the intensity of a hurricane?” Makris said “yes，in theory at least” It was a commonly known fact that wind speed has something to do with underwater noise. But it was not until Makris me that the idea occurred to him to use that relationshiD to measure hurried !

　　looking for specific evidence to support the theory. He thought there may have been a situation where a hydrophone was deployed for some other purpose and unintentionally recorded hurricane noise. And he found it. In 1999, a hydrophone in the middle of the Atlantic，just under a kilometer below the surface was listening for underwater earthquakes when a hurricane passed over it. The hydrophone picked up a low rumbling sound, like the thundering sound，from the churned up water. And on the same day, a plane had flown into the hurricane and made direct wind speed measurement When Makris compared the data, he found that there was almost a perfect relationship between the power of the wind and the power of the wind-generated noise. And there was less than 5 percent of error，which is about the same as the errors you get from direct measurements from airplane measurements.

　　1. What is the main purpose of the discussion?

　　(A) To describe the design of hydrophones used by hurricane researchers

　　(B) To introduce a new approach to measuring the power of hurricanes and cyclones

　　(C) To explain how meteorologists study the causes of hurricanes and cyclones

　　(D) To discuss factors that determine the wind speed of hurricanes and cyclones

　　2. According to the professor, what is one benefit of hurricane monitoring airplanes?

　　(A) They help meteorologists determine the storms path.

　　(B) They can gather all necessary information in just a few flights.

　　(C) Their equipment is not as sophisticated as a new technology，

　　(D) They can provide direct measurements of wind speed.

　　3. What are two advantages of using a hydrophone to measure hurricane intensity? Click on two answers (A) They can transmit underwater sounds to airplanes，

　　(B) They can lower the cost of monitoring hurricanes.^

　　(C) They can be set up before a hurricane reaches an area

　　(D) They can be installed close to the surface of the oceans

　　4. What does the professor imply about the relationship between the two researchers he mentions?^

　　(A) It will likely lead to other breakthroughs in meteorology.^

　　(B) It demonstrates the importance of interdisciplinary collaborations.^

　　(C) It developed over many years of working in the similar fields

　　(D) It led to the invention of an underwater microphone.^

　　5. Why does the professor mention a hydrophone listening for underwater earthquakes?^

　　(A) To point out the fact the underwater earthquakes are hard to detec

　　(B) To help explain how hydrophones work^

　　(C) To point out that different types of hydrophones exists

　　(D) To provide the validation of a new technique^

　　6.Listen again to part of the discussion. Then answer the question.^ Why does the professor say this，

　　(A) To emphasize the point he made earlier^

　　以上就是为大家整理得“托福听力考试机经2018年”，希望通过上述内容的整理，能够帮助大家更好的来备考托福听力考试，争取在考试中能够拿到高分成绩。