Retroactive Eavesdropping: A New Reality?

A team of scientists from MIT, Adobe Systems Incorporated (NASDAQ:ADBE) and Microsoft Corporation (NASDAQ:MSFT) have discovered a way to recover audio from video recordings by analyzing the tiny vibrations of objects, even if they are in a sound-proofed room.

Retroactive Eavesdropping: A New Reality?

Much as our ear drum vibrates when it is hit by a sound wave, objects are made to vibrate at such tiny amplitudes that the human eye cannot perceive it. However if these vibrations are recorded on a camera of suffiently high quality, sound can be reproduced. This is where the high speed video camera comes in.

The paper details greater success with high speed video cameras of up to 6000 frames per second, but comprehensible audio has also been recovered from commercial video cameras which record at 60 frames per second.

According to the research team, this “allows us to turn everyday objects — a glass of water, a potted plant, a box of tissues, or a bag of chips — into visual microphones.”

Retroactive eavesdropping: A new frontier in surveillance?

The scientific principles at work here are similar to those of laser microphones, which use light to analyze sound vibrations.

The major difference is that this new method could enable eavesdropping long after an event, so long as the video file was of sufficient quality and source audio was sufficiently loud. It is not difficult to imagine the paper generating great interest from intelligence agencies eager to increase their surveillance powers.

Commentators claim that US intelligence already possesses equipment capable of listening in to sound proof locations using “reflected electromagnetic signals to detect audible sound,” but the question is whether the MIT paper reveals a way of retroactively eavesdropping.

Retroactive eavesdropping: A viable option?

In order for the technology to be trusted for surveillance operations a lot of development still needs to happen.

As it stands, the paper presents a very interesting advance in the field, but it will presumably be a while before the first ne’er-do-well is betrayed by a high quality video recording of a potted plant.

The paper is to be presented at the computer graphics conference SIGGRAPH 2014 in mid-August.

Retroactive eavesdropping: Passive Recovery of Sound from Video