[Animats]

There was a IEEE Signal Processing Society student competition to do this in 2016.[1] I've been trying to find the results of the competition, but the relevant links are dead. The Internet Archive may be able to help.

It takes hundreds of seconds of data to see power line frequency changes on a major grid. All that synchronous rotating machinery attached to the grid has to physically change speed slightly, and there's huge inertia. Here's data for the UK national grid.[2] (This is supposed to be live, but is 2 days old.) It looks like the control systems are set up to take action at 0.1Hz error, because the frequency wanders around in that range, but as soon as it gets outside, there's a speedup or slowdown to get it back in bounds.

Claims made about short audio samples are probably bogus.

[1] https://sigport.org/sites/default/files/Information%20on%20t...

[2] https://gridwatch.co.uk/frequency