STEM与日常科技·英语30篇（9）

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降噪耳机如何安静世界

Microphones outside each earcup pick up ambient noise like traffic or airplane hum.
A digital chip analyzes sound waves in real time and generates inverse-phase signals.
When original and inverted waves meet, they cancel each other through destructive interference.
This works best for constant low-frequency sounds, not sudden high-pitched noises like alarms.
Passive insulation from earcup padding adds another 15–20 dB of quieting on its own.
Battery power enables active processing, so turning it off reduces effectiveness significantly.
Some models adapt cancellation strength based on whether you’re walking, sitting, or flying.
Newer versions use AI to predict noise patterns and adjust faster than older analog systems.