Chaotic feature of water swallowing sound signal revealed by correlation dimension

When a person drinks some water, the water will flow via pharynx, esophagus, cardia of stomach and finally into stomach. In the process, the sound produced is called water swallowing (WS) sound. The chaotic feature of WS sound signal was investigated. WS sounds acquired with an acoustic pickup attached to the abdominal walls of healthy subjects and analyzed with a computer-aided sound analysis program. Phase space was reconstructed from the sound signal time series of 5 episode WS sound signals and attractors were plotted. Correlation dimensions (CD) of the attractors in 4-dimension phase space were calculated. All attractors exhibited complex pattern as strange attractors and all CD values were non-integer. The dynamic behavior of the WS sound signals of normal subjects was chaotic.