STEM与日常科技·英语30篇（7）
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How Noise-Canceling Headphones Protect Hearing
主动降噪耳机如何保护听力
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Noise-canceling headphones use microphones to detect incoming sound waves before they reach your ears.
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A processor then generates inverse sound waves—equal in amplitude but opposite in phase—to cancel them out.
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This active method works best on steady, low-frequency noises like airplane engines or air conditioners.
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Higher-pitched sounds, such as voices or alarms, are reduced less effectively but still quieter than normal.
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By lowering background noise, users avoid turning up volume excessively to hear music or calls clearly.
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Studies show people using ANC headphones listen at average levels 8–12 dB lower than without them.
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Battery-powered circuits enable real-time adjustments as environments change—like walking from street to subway.
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Combined with passive isolation from earcup design, ANC provides dual-layer hearing protection.
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Long-term use at safe volumes helps prevent noise-induced hearing loss, especially among young adults.
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Still, they shouldn’t replace hearing protection in extremely loud workplaces like construction sites.