3 HN users recommended this explainer2 months2022–2025score 2
Years with an HN recommendation, 2007–2026
The go-to short, accessible explainer for mains hum forensics, linked whenever recording authenticity or timestamps come up.
Tom Scott explains Electrical Network Frequency analysis, where hum from the power grid in a recording is matched against grid logs to date and place it. He talks to a researcher and sets them a challenge.
“less detailed but pretty accessible video [1] explaining how mains hum forensics work” (HN, 2023)
If you haven't already seen tom Scott's video on background noise giving the location of a recording due to power line frequencies being subtly different I recommend it. [this video]
Background power-line frequency reveals recording location and time
If this is interesting to you or your kids, here's a less detailed but pretty accessible video [1] explaining how mains hum forensics work, complete with British accent. [1] [this video]
Accessible explanation of how mains hum forensics work
According to a Tom Scott's video[1], you can use background noise emitted by electricity to prove that a recording has been taken at a certain time and place. [1]: [this video]
Background electrical noise can prove when and where a recording was made
I'm writing a open-source library ( [link] ) and a webapp ( [link] ) that detects the Utility Grid noise emitted by electrical devices (A/C, motors, appliances ...) from Video/Audio recording. It then tries to date the recording by matching it to historical data. The signal processing part is getting decent. I'm still trying to collect more reference signals in RU, UK, China and Japan. Tom Scott made a video about the idea: [this video]
Video about the idea behind commenter's own project
Probably not practical but there was an interesting video by Tom Scott where investigators used the electrical hum background noise to determine when something was recorded. Maybe there is a way to audio record something to prove location. [this video]
Electrical hum used to determine when something was recorded
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