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A device sold to clear teenagers from shop doorways emits a tone at 17.4 kHz — audible only while the top of your hearing survives. A standard audiogram stops at 8 kHz and never looks there. https://thirtytwo.fyi/share/dispatch-02/
A device sold to clear teenagers from shop doorways emits a tone at 17.4 kHz — audible only while the top of your hearing survives. A standard audiogram stops at 8 kHz and never looks there. https://thirtytwo.fyi/share/dispatch-02/