Detecting Edited Audio
Interesting development in forensic analysis:
Comparing the unique pattern of the frequencies on an audio recording with a database that has been logging these changes for 24 hours a day, 365 days a year provides a digital watermark: a date and time stamp on the recording.
Philip Harrison, from JP French Associates, another forensic audio laboratory that has been logging the hum for several years, says: "Even if [the hum] is picked up at a very low level that you cannot hear, we can extract this information."
It is a technique known as Electric Network Frequency (ENF) analysis, and it is helping forensic scientists to separate genuine, unedited recordings from those that have been tampered with.
Dr Harrison said: "We can extract [the hum] and compare it with the database - if it is a continuous recording, it will all match up nicely.
"If we've got some breaks in the recording, if it's been stopped and started, the profiles won't match or there will be a section missing. Or if it has come from two different recordings looking as if it is one, we'll have two different profiles within that one recording."
Posted on December 12, 2012 at 12:59 PM • 29 Comments