The hidden background noise that can catch criminals
Tom ScottYouTube ↗
Further reading 1
Caption notes
Forensic analysts compare variations in a recording’s mains hum with an independently recorded grid history. In one sample the fundamental is hard to see but its harmonic leaves a visible trace for comparison.
Archived captions (transcription method unspecified) ↗Original passages · 2
record the grid frequency datawe'll be able to see the harmonic component around 100 hertz.