If you were ever in any doubt as to just how mind-bogglingly impressive science can be, just watch this video of a linguistic expert time-stamping phone calls using the background hum on a line.
The video, from YouTuber Tom Scott, features University of York research associate in the Department of Language and Linguistic Science, Amelia Gully, using a technique called Electrical Network Frequency analysis (ENF) to match background hum recordings with data from the UK’s power grid (it’s broken down in more detail in the video, but it essentially involves writing code that matches the recorded hum of the call with the publicly available grid logs).
“Like any forensic analysis, this isn’t some magic tool that always works,” Scott explains. “Compression can stop it working, you need minutes of uninterrupted audio to have enough confidence in the result, and sometimes there might be no background mains hum at all. But I love this, because it’s an accident of technology that’s created a tool that would sound like science fiction 20 years ago.”
