Basic Acoustic Considerations of Ear Canal

This publication contains a review of several acoustic investigations in which the effects of probe location on real-ear gain were examined through theoretical models based on acoustic properties of the average human ear and ear simulator studies. The results of these investigations are used to demonstrate the effect of standing waves and eardrum impedance on probe measurements made in the ear canal. Investigations were also conducted in the sound field with a KEMAR manikin. A commercial probe microphone system was used to measure the SPL and real-ear gain at various locations with the KEMAR ear canal. The results emphasize the critical effect of probe location on absolute or relative ear canal measurements and indicate the necessity to establish clinical procedures for probe measurements based on relevant acoustic principles.