ENF Reference Database
Definition
A continuously maintained archive of grid frequency measurements recorded at high temporal resolution, used as the ground truth against which a recording's ENF trace is compared. Examples include the Georgia Tech ENF Database and the UK National Grid Power Quality Monitoring recordings.
- Purpose
- Ground truth for comparing a recording's ENF trace
- Content
- Grid frequency measurements at high temporal resolution
- Examples
- Georgia Tech ENF Database, UK National Grid Power Quality recordings
- Field
- Audio forensics, electric network frequency analysis
Common questions
How is an ENF reference database actually used in an audio dating case?+
The examiner extracts the ENF trace embedded in a recording's mains hum and cross-correlates it against the stored grid frequency history to find the time window where the two patterns align, which dates and can help authenticate the recording.
What limits the usefulness of an ENF reference database?+
Coverage varies by region and era: a database built for one national grid cannot reliably date recordings made on a different, unsynchronised grid, and gaps in historical archiving can leave some time periods unmatched.
Related terms
- Cross-Correlation
- A statistical measure of the similarity between two time series as a function of a time lag. In ENF matching, the extracted...
- Electric Network Frequency (ENF)
- The instantaneous frequency of the alternating-current mains supply, nominally 50 Hz in most of the world and 60 Hz in North America....
- Camera Flicker / Optical ENF
- The periodic brightness variation captured in video recorded under mains-powered fluorescent or LED lighting. The lighting modulates at 100 Hz or 120...
- ENF Discontinuity
- A break in the continuity of the extracted ENF trace that is inconsistent with the reference database. Can indicate a deletion (missing...
- ENF Splice Detection
- Using breaks or discontinuities in the ENF time series to identify edits, cuts, or inserted segments in a recording. A genuine unedited...
- Geographic Grid Disambiguation
- The process of determining which national or regional grid a recording's ENF trace came from, since the 50 Hz grids of continental...
- Short-Time Fourier Transform (STFT)
- A signal processing technique that applies a Fourier transform to successive short windows of a signal, producing a time-frequency representation. Used in...
- Transmission System Operator (TSO)
- The entity responsible for operating a high-voltage electricity transmission network in a given country or region. TSOs log grid frequency in real...
Explained in these topics
- Audio Authentication and the Electric Network Frequency Method
- Electric Network Frequency Analysis for Audio DatingA continuous time-series log of grid frequency measurements maintained by a grid operator or forensic research group. Used as the ground truth against which a...