The anacoustic zone, also known as the zone of silence, is the region of Earth's atmosphere above 160 km (100 mi) where distances between rarefied air molecules are so great that sound waves can no longer propagate. With increasing height, high-frequency (short-wavelength) sounds disappear first, and only lower tones can be heard.
Related categories• AERODYNAMICS AND AERONAUTICS
• ATMOSPHERIC PHENOMENA AND STRUCTURES
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