An automated approach to the Electric Network Frequency (ENF) criterion - Theory and practice

Abstract

A relatively recent forensic technique developed to help establish the authenticity of audio and video recordings is the Electric Network Frequency (ENF) criterion. This paper confirms the applicability of the ENF criterion for use in mainland UK and describes an automated approach to matching ENF estimates taken from a questioned recording to a database of ENF values. It will be shown that the automated approach has the added advantage of producing statistical data capable of indicating the strength of the match. Consideration has been given to the robust extraction of ENF signals from evidential recordings and the resulting system and signal processing procedures outlined have been used successfully by the Metropolitan Police Forensic Audio Laboratory in London to extract and match ENF data from evidential recordings to an ENF database.