五、阅读理解
It may sound strange，but many people play noise to help themselves sleep better. Actually，this kind of noise is called coloured noise，such as white noise，pink noise，and brown noise.
Coloured noise includes a wide range(范围)of frequencies(频率). However，it shows stronger intensity(强度)at certain frequencies. For example，violet noise has stronger intensity at higher frequencies. Brown noise produces deeper sounds such as heavy rainfall，because it shows stronger intensity at lower frequencies. White noise has equal intensity across all frequencies. Typical examples of white noise are the noise made by fans，and natural sounds like gently running water. Pink noise is similar to white noise but has stronger intensity at lower frequencies.
There have been several experiments on the effect(影响)that noise has on people. In a study，10 people in New York City showed improved sleep quality and sleep duration(时长)when white noise was played. Another sleep study showed that 16 adults actually improved their memory of vocabulary after listening to pink noise in their sleep，though the effect of pink noise on sleep quality wasn't proven. Some people suggest that brown noise is the best noise for their sleep. However，no studies have proven it.
So why do some people sleep better with certain coloured noise? There are some theories(理论)that can explain it. One is about sound masking(掩蔽)，and it shows that white noise masks other noise，leading to a better sleep. Another theory is that this effect could be an example of classical conditioning(条件反射). For example，people who sleep better with brown noise may have developed the habit of falling asleep easily.
Every coloured noise has its advantages. It is your personal choice to decide which coloured noise is the best for you to get a good sleep!
()1. According to the passage，coloured noise .
A. shows similar intensity
B. is mainly created by people
C. has different frequencies
D. is harmful to people's health
()2. Which of the following is right for the frequencies of coloured noise?

()3. What can we learn from the passage?
A. White noise is helpful for people to improve memory.
B. The effect of pink noise on sleep quality has been proven.
C. People may sleep better with brown noise if they get used to it.
D. People can't decide which coloured noise to play for their sleep.
()4. What's the best title for the passage?
A. Coloured Noise：A Good Helper for Your Sleep
B. Coloured Noise：A Creative Idea to Study Sounds
C. Coloured Noise：A New Way to Improve Memory
D. Coloured Noise：A Smart Choice for Your Health