Raw audio signal (above) detected during a C1-2 HVLA thrust manipulation and the corresponding spectrogram (below). The colors are normalized to the maximum value of the spectrogram in that time epoch (red high amplitude, blue-green low amplitude). The three identified pops are visible as red vertical lines and are indicated with arrows.
Dunning et al. BMC Musculoskeletal Disorders 2013 14:24 doi:10.1186/1471-2474-14-24