Middle ear resonance in infants: Age effects

INTRODUCTION  The resonant frequency is the probe frequency in which susceptance is 0 due to the neutralization of the forces of mass and stiffness components that control the middle ear. This frequency can be evaluated by multifrequency tympanometry, and the normality value for adults ranges 800-1,200 Hz. Studies about resonant frequency in children are scarce. AIM  Identify the variation of the resonant frequency in infants between the first days after birth and the third month of life. METHOD  Prospective study. Thirty newborns were evaluated at 2 different times: at the neonatal phase up to 12 days of life, and between 72 and 84 days of life. In the first evaluation, we carried out otoacoustic emissions and identified the resonant frequency, and identified the resonant frequency again in the second evaluation. RESULTS  In the first evaluation, we determined a mean resonance value of 250 Hz for both ears, while that in the second evaluation was 385 Hz. In both assessments, we found no significant differences between the ears. There was a significant difference between the first and second evaluation. CONCLUSION  The middle ear resonant frequency in infants is lower in the first days of life due to the influence of the mass component. The present study demonstrated that the resonance frequency increased in the first months of life.