Professional footballers beware: the argument you are having with your coach could soon be overheard even within the cacophony of a packed stadium. A new microphone system allows broadcasters to zoom in on sounds as well as sights, to pick out a single conversation.

Physicists Morgan Kjølerbakken and Vibeke Jahr, formerly at the University of Oslo, Norway, were working on sonar technology when they came up with the idea for what they call a supermicrophone, now dubbed the AudioScope. The device is made up of around 300 microphones arranged in a fixed circular array above the sports ground. They are used in conjunction with a wide-angle camera that can zoom in to any position on the pitch. Because the camera is also fixed, it can be calibrated to zoom in to any location within its range.

The AudioScope software then calculates the time it would take for sound emanating from that point to reach each microphone in the circular array, and digitally corrects each audio feed to synchronise them with that spot.

“If we correct the audio arriving at three microphones then we have a signal that is three times as strong,” says Kjølerbakken. Doing the same thing with 300 microphones can make a single conversation audible even in a stadium full of sports fans (see video).

Kjølerbakken and Jahr have now patented the device and founded a company – Squarehead Technology – to develop their idea. The most obvious application is in televised sports, and the company has been working with basketball and soccer teams to test it out. The response has been good, says Kjølerbakken, although some players aren’t keen on the idea.