Can synchronized otoacoustic emissions really be attributed to SOAEs?

In this study, spontaneous and transiently evoked otoacoustic emissions (SOAEs and TOAEs, respectively) were recorded in 15 normal-hearing subjects. An analysis of the TOAE spectrum was performed with three time intervals: 20 ms-40 ms, 40 ms-60 ms, 60 ms-80 ms (the spectra found are labelled TOAE2-4, TOAE4-6, TOAE6-8). The frequencies of the peaks observed were compared to the SOAE frequencies. We found that 78.8% of the TOAE peaks also were observed as SOAEs and 91.2% of the SOAE peaks were recorded in the TOAE2-4 spectrum. Peaks that were not observed by either method had lower amplitude than the others, and SOAE peaks that were not in TOAE2-4 spectrum had higher frequencies than those that were observed in the TOAE2-4 spectrum. We conclude that the TOAE spectrum recorded after 20 ms does not include all of the SOAE frequencies and is not composed solely of SOAEs. Therefore, frequencies exist which are synchronized specifically to the stimulus and SOAEs exist which can't be synchronized more than 20 ms.