Audible gamma radiation spectroscopy
Channel: Carl Willis
Date: 2012-11-22

Since we cannot directly see gamma rays and perceive their energies as colors as we can with a prism or a grating spectrometer for visible light, they must be observed instead by detectors.  Typically, gamma radiation energy data obtained from detectors are interpreted on a pulse height histogram.  The features of such energy spectra are well-known: "photopeaks," "Compton edges," "backscatter peaks", "sum peaks", "escape peaks," and so forth, all representative of the physical processes that occur when the radiation interacts with matter in and around the detector.  Some of these interactions don't occur at all with visible light.  

But here's a new sensory direction, inspired by the phenomenal efforts of the Swedish guys at http://www.radioactiveorchestra.com: interpreting gamma radiation energies through auditory means.  My own approach is illustrated in this video.  Pulses from an NaI:Tl scintillation detector are digitized in a standard NIM MCA over 20-ms intervals, and then in a little LabVIEW VI, the most frequent pulse height is linearly mapped to musical key on a 12-tone equal-temperament scale and written to the sound output buffer on the computer.  Low gamma energies and events that deposit small amounts of energy (Compton scattering, for instance) produce low pitches, and high energies produce high pitches.  Additionally, my program scales audio volume according to the total number of counts received in the 20-ms interval.  High count rates (strong radiation fields) result in loud notes, and low count rates (background, and weak sources) are quieter.

Please feel free to suggest improvements or point out ways I might make this work better.  One of the major deficiencies has to do with underflow on the audio buffer because synthesizing the output tone waveforms is too time consuming.  You can hear some artifacts from this, as well as some undersampling, some popping and clicking, and some other lameness in the audio.  I'm trying to make it better, but you should go check out the video TedX talk in Goteborg given by the Radioactive Orchestra guys if you want to hear a professional approach to this idea.

http://www.youtube.com/watch?v=Eas4p8Sob9E