Tympanometry is a method of measuring the compliance of the tympanic membrane and the middle ear pressure of the eardrum and of diagnosing the existence of middle ear storage liquid. Tympanometry using a probe sound of 226 Hz has generally been used, but it shows an A-type tympanogram in neonates with a soft external auditory canal even if there is middle ear storage liquid, owing to a change in pressure. On the other hand, there is a report showing that tympanometry using a probe sound of 1,000 Hz is more reliable. In this study, we compared and examined the differences between the impedance audiometers RS-22 and GSI Tympstar Version 2 with probe sounds of 1,000 and 678 Hz in our institution. Eleven ears showed the A type when using a probe sound of 226 Hz and the B type when using probe sounds of 1,000 and 678 Hz. All 11 ears were those of babies less than twelve months of age. Our results indicated that tympanometry with probe sounds of 1,000 and 678 Hz is useful for babies less than 6 months of age. The probe sound of 1,000 Hz showed artifact-like waveforms and reexamination is needed. GSI requires time for apparatus operation because it is of the syringe type. These results indicated that its measurement was difficult for children who cannot keep still. An audiometer with the structure and function that can fix an earplug and have the probe sound of 1,000 Hz and with the pump type is required.
