Relevance of animal models to the clinical application of otoacoustic emissions

The above discussion reveals that there are some significant differences in the basic properties of OAEs measured in the ears of primates and the small mammals. The 2f₁-f₂ DPOAEs are around 30 dB smaller in humans and monkeys than in the small mammals. In contrast, TEOAEs and SFOAEs are around 30 dB larger in humans and monkeys than in the small mammals. The low-level SOAEs, observed in approximately 50% of human ears, appear to be uncommon in the small mammals. This observation is consistent with the hypothesis that these SOAEs arise due to feedback of the TEOAE/SFOAE generator output into its input, and that, in the small mammals, this generator's output is too weak to sustain a feedback oscillation, as it appears to do in primates. Additionally, the few SOAEs reported in small mammals appear to correspond to the rare, atypical SOAEs reported in human ears. The different properties of the atypical SOAEs and their apparent association with pathology suggests that the mechanism of generation of these SOAEs in both humans and small mammals may be different from that of the typical SOAEs observed in primate ears.