The magnitude of random errors in acoustic rhinometry and re-interpretation of the acoustic profile

By measuring the effect of incomplete acoustic seal and increasing nosepiece insertion depth on the derived nasal acoustic profile, this study quantifies the random errors that may arise in the course of the clinical practice of acoustic rhinometry using the insert nosepiece. The relative movement of the nose and nosepiece also enables us to separate the contribution of each to the acoustic curve. Sixteen volunteers were tested using a commercial rhinometer. As a consequence of this study we are able to formulate the following conclusions: (1) The first minimum of the nasal acoustic profile is due to the end of the nosepiece, but may be further diminished by the position of the nosepiece tip on or within the nose. (2) The second minimum is due to the nasal valve, to which the head of the inferior turbinate contributes. (3) Acoustic rhinometry is extremely sensitive to acoustic leaks and results obtained without a fluid acoustic sealant cannot be considered valid. (4) The errors associated with the nosepiece insertion technique are very small unless the nosepiece is forced into the nasal vestibule.