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The hidden background noise that can catch criminals

Tom Scott · explainer · Watch on YouTube

Power grid, heating & buildingsPrivacy, surveillance & cybercrimeLaw, policing & justice

What it is

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.

Why Hacker News recommends it

The go-to short, accessible explainer for mains hum forensics, linked whenever recording authenticity or timestamps come up.

  • 3 people recommended it
  • 2 different months
  • 0 strong recommendations
  • first 2022, last 2025

What HN commenters said

  1. “background noise giving the location of a recording due to power line frequencies being subtly different I recommend it.”

    Background power-line frequency reveals recording location and time

    AnotherGoodName, 2022-08 · Recommendation · in “Extracting Audio from Visual Information”

  2. “less detailed but pretty accessible video [1] explaining how mains hum forensics work”

    Accessible explanation of how mains hum forensics work

    subpar, 2023-02 · Recommendation · in “How to date a recording using background electrical noise”

  3. “I really enjoy Tom Scott. Everything he puts out is wonderfully concise.”

    Concise video on the same subject

    Groxx, 2023-02 · Recommendation · in “How to date a recording using background electrical noise”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: enf analysis, mains hum, forensics, power grid, recordings

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