Prism Forensics LLC Presents at the 46th AES Forensic Audio Convention

Sherman Oaks, CA, June 24, 2012 --(PR.com)-- The 46th AES Convention on Forensic Audio was held over the weekend in Denver Colorado. Sean Coetzee, forensic consultant and owner of Prism Forensics LLC presented a peer reviewed study on digital audio authentication titled “Phase & Amplitude Analysis of the Electric Network Frequency” published in the “Proceedings of the AES 46th International Conference.” Extensive research has been conducted in the field of forensic audio authentication and one method which has proven to be considered reliable is the ENF criterion. Audio recorders will often pick up the hum present in the electric power grid and it will embed itself in the recording. This hum fluctuates very slightly overtime in an unpredictable manner, creating what we could call a natural watermark in the recording. This hum also called Electric Network Frequency (ENF) can be extracted from the recording and compared to a reference ENF from an official database. If the recording is authentic both signals will be identical, any discrepancies between the two would indicate potential tampering of the recording.

At this time examiners may not have access to official ENF databases as this is a fairly new procedure. It was therefore necessary to develop methods that would enable the detection of edits within the ENF without the need of a reference database. The ENF is a continuous sine wave, in other words a signal formed of peaks and valleys, following each other by exactly the same amount. Any discrepancies between the peaks and valleys could indicate a potential edit within the recording. The discrepancies are usually very small and undetectable to the naked eye. The method proposed in Sean Coetzee’s study enables easy, quick and accurate visualization of potential phase breaks. When phase discontinuity occurs in the recording a decrease in amplitude will be present within the vicinity of the phase break. Using various down sampling and filtering procedures these amplitude changes can be easily detected in a time series window (oscilloscope) and help reinforce the examiners opinion in regards to the authenticity of the recording.

With the constant development of digital audio technology the need for such conventions is paramount. It’s an opportunity for the forensic audio community to work together in developing new methods in regards to forensic audio analysis. By bringing our research together we are creating standardization within the industry and demonstrating the reliability of our science.

Sean Coetzee is the owner of Prism Forensics LLC which provides audio enhancement and authentication analysis. He is a graduate of Brighton University, UK with a BA in Music Production and a professional sound engineer, having worked in studios in the UK, France and the USA. He is a listed expert with the Los Angeles Superior Court and a certified forensic consultant with the American College of Forensic Examiners Institute (ACFEI).