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Part III Reading Comprehension (40 minutes)
Task 1
About 23 million headset stereos are sold in the United States each year. Most have one thing in common: they can cause hearing loss.
Studies have shown that sound levels from the machines can reach 115 decibels(分贝) or more — roughly equivalent to standing 100 feet from a commercial jet at takeoff. At the level, permanent hearing damage can occur after just 15 minutes. And the earlier a child begins using a headset, the more damage can accumulate. Loud noise causes hearing loss by killing irreplaceable hair cells in the inner ear. Normally, the process occurs slowly as people age, but noise damage can accelerate it.
Noise-induced hearing loss is insidious(不知不觉中发展的)；damage may not be apparent until later in life. Since headsets are used privately, parents often don't realize how loud their children's music is.
As a rule, experts say headset sound loud enough to be heard by passers (approximately 100 decibels) can cause damage if used more than two hours a day. The allowable time is halved for every five decibels above that. For example, at 105 decibels, the maximum is one hour.
Whatever your age, noise is dangerous if it hurts your ears, makes them ring or causes you to shout above it to be heard.
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