Well, that's the very specific command I'm using in one of my webapps (https://datethis.app), and it's one of the main performance hotspots, so it's very *not* immaterial.
To compare any given piece of sound with reference sounds for ENF analysis, the references must have been recorded to start with.
The fact that a webapp like yours can exist... does it mean that we, indeed, have recordings of electrical hum spanning years and years? Are they freely available, or are they commercial products?
It seems so crazy to me that someone decided to put a recorder next to a humming line just to be able to later in the future match the sound with some other recordings...
For US, I couldn't find any open dataset. For these regions, I'm basically recording the sound of an A/C motor to get the reference data, but I only have a few months of backlog.
See here for the coverage of the webapp: https://datethis.app/coverage