Standard and multifrequency tympanometric norms for Caucasian and Chinese young adults

This study examined differences between a group of normal-hearing Caucasian and Chinese young adults on six tympanometric parameters. The goal of this study was to determine if the Chinese group had different low and multifrequency tympanometry results than the Caucasian group.

There were a total of 159 subjects (303 ears) between the ages of 18 and 34 years, with 76 subjects in the Caucasian group and 83 subjects in the Chinese group. Tympanometric data were gathered on a clinical immittance machine, the Virtual 310 equipped with a high frequency option. Four of the parameters-static admittance (SA), tympanometric width (TW), tympanometric peak pressure (TPP), and ear-canal volume (ECV)-were measured automatically at a standard 226 Hz frequency. The remaining two parameters-resonant frequency (RF) and SA up to 1,200 Hz-were measured by multifrequency, multicomponent tympanometry, using a mathematical approach.

The Chinese group had significantly lower SA, wider TW, more positive TPP, and lower ECV than their Caucasian counterparts. The parameter of SA up to 1,200 Hz showed a significant group effect (Caucasian versus Chinese) until 900 Hz in the male group and up to 1,120 Hz in the female group. The Chinese group had significantly higher RF than the Caucasian group. Once the effect of body size was compensated by adjusting for the ear canal and the middle ear volumes, the differences observed between the Caucasian and the Chinese groups were no longer significant for tympanometric parameters obtained at standard probe tone frequency of 226 Hz; however, the effect was still significant for SA obtained at higher probe tone frequencies (560, 630, 710, 800, and 900 Hz) and for RF. Applying the Caucasian norms to a group of mainly Caucasian adults with surgically confirmed otosclerosis resulted in improved overall test performance when compared with the combined Caucasian and Chinese norms and the Chinese only norms.

It seems that the body size plays a crucial factor in the observed differences between the Caucasian group and Chinese groups at a standard probe tone frequency of 226 Hz; however, other mechano-acoustical properties of the middle ear may contribute to these differences at higher probe tone frequencies. Findings of this study suggest that further research is needed to investigate the effects of body size on immittance measures with other ethnic groups. In the meantime, overall test performance may be improved by using a more homogenous norm when testing the Caucasian or Chinese individuals.