https://en.wikipedia.org/wiki/Electrical_network_frequency_analysis https://en.wikipedia.org/wiki/Electrical_network_frequency_a... Electrical network frequenc

https://en.wikipedia.org/wiki/Electrical_network_frequency_analysis https://en.wikipedia.org/wiki/Electrical_network_frequency_a... Electrical network frequency (ENF) analysis is an audio forensics technique for validating audio recordings by comparing frequency changes in background mains hum in the recording with long-term high-precision historical records of mains frequency changes from a database. The technology has been hailed as "the most significant development in audio forensics since Watergate."