Digital audio recording analysis: the Electric Network Frequency (ENF) Criterion


  • Catalin Grigoras Ministry of Justice, Bucharest



electrical network frequency criterion, forensic audio, forensic acoustics, audio authentication, digital audio recordings


This article reports on the Electronic Network Frequency Criterion as a means of assessing the integrity of digital audio evidence. A brief description is given of phenomena that determine ENF varaiations. In most situations,to reach a non-authenticity option, the visual inspection of spectrograms and comparison with an ENF database are enough. A more detailed investigation, in the time domaine, requires short time windows measurements and analyses. The stability of the ENF over geographical distances has been established by comparison of synchronized recordings made at different locations on the same network. A real case is presented, in which the ENF Criterios was used to investigate an audio file created with a secret surveillance system. By applying the ENF Criterion in forensic audio analysis, one can determine whether and where a digital recording has been edited, establish whether it was made at the time claimed, and identify the time and date of the registering operation.

Author Biography

  • Catalin Grigoras, Ministry of Justice, Bucharest
    Catalin Grigoras is a forensic expert with the National Institute of Forensic Expertise, Ministry of Justice, Bucharest, Romania. He has a PhD in audio signal processing and is presently involved in developing new techniques for forensic audio analysis. His previous work includes studies on voice analysis, digital audio recording authentication and noice-reduction algorithms. He is also assistant professor in the Faculty of Law at Babes-Bolyai University, Cluj, Romania, where he teaches forensic science and examinations. He is a member of the International Association of Forensic Phonetics and Acoustics, the American College of Forensic Examiners and the American Board of Recorded Evidence.






How to Cite

Grigoras, C. (2005). Digital audio recording analysis: the Electric Network Frequency (ENF) Criterion. International Journal of Speech, Language and the Law, 12(1), 63-76.