Frequency analysis is helping forensic scientists separate genuine audio recordings from those that have been tampered with.

Mains electricity emits a constant hum, known as the ‘mains frequency’, which becomes embedded in digital recordings made anywhere near an electrical power source. This noise is being used to help police in the UK fight crime, as forensic scientists can authenticate audio evidence to find out whether it is genuine or has been edited.

BBC News reports that audio specialists at the Metropolitan Police forensic lab in south London have been continuously recording the sound of mains electricity for the last seven years. Minute fluctuations have been found to occur and the pattern of these changes in frequency is unique over time.

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