How we perceive acoustic pitch could be due to a physical phenomenon rather than, as was previously thought, how our brains process auditory information, reports a study published online this week in Nature Physics. These findings can be used to make detailed predictions about pitch sensation, which are corroborated by previously unexplained data from decades-old psychoacoustic experiments.

Florian Gomez and Ruedi Stoop reveal that a key factor determining the way we perceive pitch lies with the fact that our cochlea is filled with viscous fluid. The authors created a mathematical model that suggests that combination tones - additional tones perceived when two tones are played simultaneously - in the presence of this fluid are responsible for pitch perception in human hearing.