Changes in Resonance Frequency and Length of External Auditory Canal in Relation to Age

Jeong, Hyang Sook; Koo, Han Eol; Lee, Sang Min; Koo, Soo Kweon; Lee, Sang Hwa; Yu, Tai Hyun

Abstract

BACKGROUND AND OBJECTIVES: With the currently available diagnostic procedure, hearing impaired children are diagnosed at an early age and hearing aids are fitted soon thereafter. Thus, appropriateness of using available correction methods for adult ears and ear models for determining and predicting hearing aid characteristics for these children need to be examined. The objectives of this study are to create a database of resonance frequency and length of external auditory canal (EAC) in all age groups and to adjust the peak frequency response of hearing aid system to take account of the changing resonance peak frequency as child gets older. MATERIALS AND METHOD: We studied 437 ears with no age limitation. We measured rear ear unaided response (REUR) with Rastronics frequency response analyzer and external ear canal length using silastic tube under microscopic or otoscopic finding. Statistical analyses were performed to determine age differences.
RESULTS
Ear canal length increased with age, and an adult value was achieved by the age of 14 years. Resonance frequency decreased with age, and reached to an adult value by the age of 9 years. There was significant relationship between ear canal length and resonance frequency.
CONCLUSION
Alteration in resonance frequency with age may have practical implications by affecting the insertion gain of hearing aid system in children. The data may be used as useful adjustment factors to correct the current hearing aid system in children.