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Noise-Canceling Headphones: Physics in Your Ears
主动降噪耳机：耳中的物理学
精读先不看文字，完整听一遍。
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Active noise-canceling (ANC) headphones use microphones to detect ambient sound waves entering your ear canal in real time.主动降噪（ANC）耳机通过麦克风实时检测进入耳道的环境声波。
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Built-in processors analyze each wave’s frequency, amplitude, and phase, then generate an inverted 'anti-noise' signal milliseconds later.内置处理器分析每个声波的频率、振幅和相位，几毫秒后生成反向的“抗噪声”信号。
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When the original and anti-noise waves meet, they interfere destructively—canceling each other out through superposition.原始声波与抗噪声波相遇时发生相消干涉，通过叠加效应相互抵消。
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Low-frequency rumbles like airplane engines or subway vibrations are easiest to cancel because their long wavelengths are predictable.低频轰鸣声（如飞机引擎或地铁震动）最容易消除，因其波长较长、变化可预测。
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Higher frequencies scatter more and change rapidly, so ANC works best alongside passive isolation from snug ear cushions.高频声波更易散射且快速变化，因此ANC需配合耳垫紧密贴合带来的被动隔音效果才能发挥最佳性能。
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Battery power runs the circuitry; turning off ANC extends playback time by up to four hours on many models.电池为电路供电；关闭ANC功能可在多数型号上延长播放时间达四小时。
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Some headphones adapt cancellation strength based on fit detection—using sensors to adjust processing for individual ear shapes.部分耳机可根据佩戴检测自动调节降噪强度——利用传感器适配不同耳形进行处理优化。
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Developers test performance using standardized acoustic manikins and anechoic chambers to measure decibel reduction objectively.开发者使用标准声学假人和全消声室客观测试降噪性能，精确测量分贝衰减量。
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While effective for travel and focus, ANC does not protect hearing from dangerously loud sudden noises like sirens or explosions.尽管ANC在旅行和专注场景中效果显著，却无法防护警笛、爆炸等突发性高强噪音对听力的损害。
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This everyday tech demonstrates wave physics, real-time computing, and human-centered engineering—all packed into a pair of earpieces.这项日常科技集波动物理、实时计算与以人为本的工程设计于一体，全部浓缩于一副耳塞之中。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- When the original and anti-noise waves meet, they interfere destructively—canceling each other out through superposition. 原始声波与抗噪声波相遇时发生相消干涉，通过叠加效应相互抵消。
- Developers test performance using standardized acoustic manikins and anechoic chambers to measure decibel reduction objectively. 开发者使用标准声学假人和全消声室客观测试降噪性能，精确测量分贝衰减量。
- Active noise-canceling (ANC) headphones use microphones to detect ambient sound waves entering your ear canal in real time. 主动降噪（ANC）耳机通过麦克风实时检测进入耳道的环境声波。
④ 懂 · 选一选
⑤ 今天会说这一句
When the original and anti-noise waves meet, they interfere destructively—canceling each other out through superposition.
⑥ 跟读并录音
When the original and anti-noise waves meet, they interfere destructively—canceling each other out through superposition.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：When the original and anti-noise waves meet, they interfere destructively—canceling each other out through superposition.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。