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Electrical network frequency analysis

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Electrical network frequency (ENF) analysis is a forensic science 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.[1]

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.[2]

The technology has been hailed as the 'the most significant development in audio forensics since Watergate.'[3]. 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.[4]

References

  1. ^ Catalin Grigoras. "Digital Audio Recording Analysis: The Electric Network Frequency Criterion" (PDF). Diamond Cut Productions, Inc.
  2. ^ Cooper, A.J: "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)
  3. ^ Chris Williams (2010-06-01). "Met lab claims 'biggest breakthrough since Watergate'". The Register.
  4. ^ Maarten Huijbregtse, Zeno Geradts. "Using the ENF criterion for determining the time of recording of short digital audio recordings" (PDF). Lecture Notes In Computer Science; Vol. 5718, Proceedings of the 3rd International Workshop on Computational Forensics, 2009.