목적: The objectives of this study are to investigate the correlation between the original DPOAE intensity and the absolute amount of suppression (SA) and to propose suppression ratio (SR) as a more reasonable index of MOC efferent function. 방법:Bilateral assessment of the effect of MOC activation on DPOAE fine was performed in 97 (n=194 ears) healthy subjects (55 females) with the age of 21-70 (mean 40) years. SA is defined as the difference between DPOAE intensities measured with and without broad band noise (BBN) contralateral stimulation at 65 dB SPL. SR is calculated with dividing SA by the DPOAE intensity without BBN. Pearson correlation coefficient was calculated for measuring the degree of dependency of SA and SR on the intensity of DPOAE without BBN. We performed one way analysis of variance to measure the difference among age groups and two sample t-test to estimate gender effect. 결과:As averaged through subjects at each measured frequency, SA showed a significant positive correlation with the level of DPOAE without BBN (r=0.46, p=0.021), whereas SR did not (r=0.14, p=0.51). The DPOAE level without BBN and SA were decreased in older subjects compared to the younger (p<0.05) but SR was not affected by age (p=0.84). Regarding the gender effect, none of them was affected (p=0.66, p=0.24 and p=0.70, respectively). 결론:The equal level of DPOAE (without BBN) between study groups is an essential prerequisite for using SA as a reliable index for presenting MOC efferent function, which might be hard to achieve in the commonplace situations of comparing heterogeneous groups. In that event, SR, instead of SA, could reflect the genuine efferent function of the MOC system. Our results suggest that MOC efferent function might not actually be affected by aging when presented by the suppression ratio since it minimizes the influence of the afferent function.