Wideband acoustic immittance in early childhood: The role of outer and middle ear in auditory development.

OBJECTIVE: To investigate essential properties of acoustic transmission, considering the influence of anatomical and functional changes on the development of the auditory system. METHODS: This is a cross-sectional observational study. Five groups were established depending on the age range of 117 normal-hearing children: 35 Newborns (NB), 15 infants aged six to eight months (6‒8 m), 10 children aged three to five years (3‒5y), 28 aged six to eight (6‒8y) and 29 aged nine to eleven years (9‒11y). Wideband Acoustic Immittance (WAI) data were recorded using a Titan tympanometer (Interacoustics®). RESULTS: The highest absorbance measurements were found in NB and 6‒8 m groups than in children aged three years and older - groups 3‒5y, 6‒8y and 9‒11y - whose measurements were quite similar to each other, being higher in the range of 2k to 6k Hz. Therefore, unlike the reduction in absorbance at low frequencies, which should occur after the first month, at high frequencies, it seems to occur only after the first six months of life. Resonance Frequency (RF) data showed a significant increase with age. In newborns, RF was lower than in infants (6‒8 m), and there were no apparent changes from the age group 3‒5y to 9‒11y. CONCLUSION: Anatomical and physiological changes in the outer and middle ear throughout childhood lead to changes in WAI measurements, such as equivalent ear canal volume and compensated acoustic admittance increased throughout childhood, while resonance frequency only increased in the first three years of life. The variable pattern of acoustic absorbance is likely representing the various structural changes throughout childhood that affect mass and stiffness components independently.