In effec the mains hum signal is treated as if it was a time-dependent [[digital watermark]] that can be used to identify the time at which the recording was created, and to help detect any edits in the sound recording.<ref> Cooper, A.J: {{cite web|url=http://www.aes.org/e-lib/browse.cfm?elib=14411|title=The electric network frequency (ENF) as an aid to authenticating forensic digital audio recordings – an automated approach}}, Conference paper, AES 33rd International Conference, USA (2008)</ref>
The technology has been hailed as the 'biggestthe breakthroughmost significant development in audio forensics since [[Watergate]].'<ref>{{cite web|url=http://www.theregister.co.uk/2010/06/01/enf_met_police/|title=Met lab claims 'biggest breakthrough since Watergate'|author=Chris Williams|publisher=The Register|date=2010-06-01}}</ref>. However, according to a paper by Huijbregtse and Geradts, the ENF technique, although powerful, has significant limitations caused by confusion based on fixed frequency offsets during recording, and self-similarity within the mains frequency database, particularly for recordings shorter than 10 minutes.<ref>Maarten Huijbregtse, Zeno Geradts. {{cite web|url=http://www.forensic.to/ENF%20processed.pdf|title=Using the ENF criterion for determining the time of recording of short digital audio recordings}} Lecture Notes In Computer Science; Vol. 5718, Proceedings of the 3rd International Workshop on Computational Forensics, 2009.</ref>
