60 kHz is “long wave”, a frequency so low you could almost still hear. It's just thrice the upper limit of ~20 kHz for the human ear. I love how my wristwatch

60 kHz is “long wave”, a frequency so low you could almost still hear. It's just thrice the upper limit of ~20 kHz for the human ear. I love how my wristwatch eats sunlight at day (solar-powered) and drinks radio waves at night. Never has to change a battery and shows time as accurately as any internet-connected device that listens to NTP.