科学素养与生活应用·英语30篇（2）
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How Noise-Canceling Headphones Create Silence
降噪耳机如何制造静音
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Active noise-canceling (ANC) headphones use microphones to detect incoming ambient sound waves.主动降噪（ANC）耳机通过麦克风检测环境声波。
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Then, built-in processors generate 'anti-noise' signals—sound waves with opposite phase and equal amplitude.内置处理器随即生成“反向声波”——相位相反、振幅相等的声波。
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When original and anti-noise waves meet, they cancel each other through destructive interference.原始声波与反向声波相遇时，通过相消干涉相互抵消。
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This works best for low-frequency hums like airplane engines or air conditioners—not sudden speech.该技术对飞机引擎、空调等低频嗡鸣效果最佳，对突发的人声效果有限。
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Passive isolation from earcup padding blocks higher frequencies, complementing ANC performance.耳罩垫层提供的被动隔音可阻隔高频声音，从而补充ANC性能。
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Battery power runs the circuitry; turning off ANC extends playback time noticeably.电路运行依赖电池供电；关闭ANC可显著延长播放时间。
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Some models adapt cancellation in real time based on fit and movement using motion sensors.部分型号利用运动传感器，根据佩戴贴合度和头部动作实时调整降噪效果。
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While effective, prolonged use at high volumes may still harm hearing—volume limits matter most.尽管效果显著，长时间高音量使用仍可能损伤听力——音量限制最为关键。