See also https://www.youtube.com/watch?v=O3Q7L0TNGtk and hear the new signals here: https://www.youtube.com/watch?time_continue=3&v=UVIGS1XvQAY&...
[MAN] at the tone. 22 hours. 8 minutes. coordinated universal time.
[TONE]
[WOMAN] follows is a scientific modulation test. for more information visit DJ NIST
The "clicks" are second markers, and the low-frequency hum that follows each click encodes a single bit of a binary datastream conveying the current time. If you've ever had an automatic clock in the US, it sets the time by tuning in to WWV and decoding this signal.
It broadcasts on longwave rather than shortwave and uses a different modulation.
https://www.nist.gov/pml/time-and-frequency-division/time-di...