STEM与日常科技·英语30篇（7）

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主动降噪耳机如何保护听力

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