When building an Electric Network Frequency (ENF) database for forensic purposes, ensuring that the recorded signal satisfies standards for forensic analysis is crucial. The ENF signal shall be free of clipping and lossy compression distortions, the signal to noise ratio shall be as high as possible, and the acquisition system clock shall be synchronized with an atomic clock. Using an ENF database to compare reference and questioned ENF involves precise measurements of amplitude, spectrum, and zero-crossings in order to accurately time-stamp, discover potential edits, and authenticate digital audio/video recordings. Due to the inherent differences in electronic components, building multiple ENF probes to create multiple databases with matching waveforms can be challenging. This paper addresses that challenge and offers a solution by using MathWorks MATLAB to calculate the best combination of components and produce graphical displays to help give a visual aid to the outcome in order to build a high quality ENF probe. This paper also addresses the challenge of establishing a fail-safe database to safely store the accurately acquired ENF information. This paper concludes that a reliable ENF database is mandatory for both scientific research and for forensic examination.
This paper costs $33 for non-members and is free for AES members and E-Library subscribers.