A medical acoustic signal analysis method based on Zipf law

We present in this paper a medical signal analysis method that we have developed in order to study, in an atraumatic and non-invasive way, the inferior oesophageal sphincter behaviour. This one plays an important part in the gastro-oesophageal reflux phenomenon. The proposed method is more efficient and is better suited to our problem than traditional signal processing methods that did not give good results. It has a double originality. The first one lies on the audio signal coding, based on its time-frequency representation, and allowing the extraction of a set of ordered words that makes up a text. The second one lies on the use of the Zipf law as an analysis tool. The parameters obtained from the Zipf law observation allow one to automatically detect and characterize signal regions of interest, which are periods corresponding to xiphoidal sounds (produced when a bolus, a small quantity of baryte, crosses the inferior oesophageal sphincter). Thus, the results permit one to evaluate the sphincter capability, which is a precious help for specialists.