THE IDENTIFICATION OF THE POTENTIAL LIMITATIONS OF ACOUSTIC RHINOMETERY USING COMPUTER-GENERATED, 3-DIMENSIONAL RECONSTRUCTIONS OF SIMPLE-MODELS

The internal surface of the nasal cavity is geometrically complicated and does not lend itself readily to direct measurement. Simple geometr ic shapes were used as a model for changes in the nasal cavity. Follow ing the introduction of specific changes to a particular system, the e ffect of these changes on the acoustic evaluation of the space was stu died. Cylinders were chosen, as the wave path could be assumed to be p erpendicular to the model surface. The acoustic rhinometer's accuracy was assessed in the presence of small and large variations in cross se ctional area, in the presence of a series of consecutive area changes, and a gradual change in diameter The effect of the introduction of ac oustic leak was also modelled The acoustic data acquired from these mo dels teas used to reconstruct the model in three dimensions. These rec onstructions were compared to the original model. The acoustic rhinome ter was found to resolve with reasonable accuracy the dimensions of sm all spaces; however, if regions of sudden large area changes were pres ent in the space, the data beyond these legions was highly unreliable. Furthermore, the presence of acoustic leak in a system had a similar effect. Unless precautions are taken in the set-up and operation of th e accoustic rhinometer, the potential for misinterpretation of data an d the introduction of bias is very high.