Last week, around 10 people from BBC A&Mi, including myself, gathered for two days of hardware hacking. The goal was to build a Rockterscale -- a device that was able to measure how much a band rocks. Since I haven't done any real-time audio processing in a long time, I decided to give that a go - analysing a live audio input and extract some of its characteristics. I used Paul Brossier's Aubio library to do so, as it seemed relatively easy to hack, and was already doing something we thought was great for visualisation purposes: beat tracking from a live audio input. After the first day, we had a bit of C code that extracted the loudness, the spectral centroid and the spectral spread from the live audio input. Then, we sent over the normalised data using Open Sound Control to the visualisation components.

But, of course, the audio signal is not the only thing to consider in order to determine how much a band rocks! We used a number of sensors to capture the reactions of the crowd:

  • The Hat of Rock, capturing some headbanging data:


  • An accelerometer under the dance-floor/mosh-pit, and a force sensor hooked on the crash barrier:


  • A webcam capturing how much movement there is in the crowd:


All the data fed by these different components was visualised on a screen: C

and on a physical rockterscale (yes, it does go up to 11 :-)) C

Here is a small video of all that into action! (I think the best part is the BBC A&Mi people dancing on Ace of Spades to try out the system :-) ).