Analysis by Sweep Frequency Impedance (SFI) Meter of 226-Hz and 1,000-Hz Tympanometries in Neonates

Conventional 226-Hz tympanometry has been acknowledged as a reliable method for detecting middle ear dysfunction in adults and children. However, its application has proved to be inaccurate in neonates younger than 7 months of age. In the present study, therefore, tympanograms of neonates were derived based on sweep frequency impedance (SFI) data and an attempt was made to investigate the reason why conventional tympanometry is inadequate for neonates. Analysis of neonatal tympanograms revealed that the application of a conventional 226-Hz probe tone leads to either a type A or a type M tympanogram. This is possibly due to the intrinsic oscillatory behavior of the external ear canal wall caused by its resonance at around 226 Hz.