## 3 Results
### Advanced DPOAE Paradigms in Exposed Individuals--Ratio Sweeps  
As outlined in the methods section, ratio sweeps were analyzed in two ways; examination of overall DPOAE level for the varied ratios and calculation of unweighted and weighted group delays. To be considered a significant change, the absolute change in DPOAE level had to be \(\geq\)6 dB between sessions for a single individual and a significant change in group delays for an individual was defined as an absolute change of 0.87 ms or more [30]. As with level sweeps, ratio sweeps were collected at the highest and second highest frequency with a present DPOAE based on the gross discrete frequency sweep, for a total of two ratio sweeps. _DPOAE Levels for Ratio Sweep at Highest Frequency with a present DPOAE._ Seven of nine patients (78%) demonstrated significant changes in overall DPOAE level for the ratio sweep collected at the highest frequency with a present DPOAE for each individual. Patients 4, 6, 7 and 9 had overall DPOAE changes across all sessions at several consecutive frequencies. Results for patient 9 are seen Figure 3 in the left panel. Patient 16 demonstrated significant changes at two consecutive frequencies from baseline to the second and final session. Similarly, patient 18 had changes in DPOAE level across several consecutive frequencies from baseline to the second (final) session. As with the other paradigms, patient 8 did not have a baseline session, but significant changes were seen from the first testing session to the last testing session at consecutive frequencies, generally at the narrower ratios (when f2 and f1 are more closely spaced). Patients 4, 7, and 16 received oxaliplatin and patients 6, 8, 9, and 18 received carboplatin. _DPOAE Levels for Ratio Sweep at Second Highest Frequency with a Present DPOAE._ Seven of eight patients (87%) demonstrated significant changes in overall DPOAE level for the ratio sweep at the second highest frequency tested with a present DPOAE for each individual. Patient 4, like many of the other paradigms, had no significant changes from baseline to the final session, but sessions two through four had significant changes that then recovered by the final session. Significant changes in DPOAEs at sessions two through four were typically at narrower ratios. The same trend for this paradigm was observed in patient 6, except with significant changes seen at wider ratios. Patient 8 (no baseline session), had present emissions during the first session but then a portion disappeared for the second session. Absent emissions for the second session were apparent at wider ratios (when there was a larger separation between f\({}_{2}\) and f\({}_{1}\)). Patient 9 demonstrated significant changes, both increases and decreases from baseline to the second (final) session at several consecutive frequencies (see Figure 3, right panel). Patients 7 and 10 had significant changes for at least two consecutive frequencies (ratios); these ratios were mostly in the wider ratio region. Patient 18 demonstrated consistent, significant changes from baseline testing to the second and third sessions; these changes were seen at different consecutive frequency ranges across the full ratio range tested. Patients 4, 7 and 10 received oxaliplatin and patients 6, 8 and 18 received carboplatin. Overall, six patients demonstrated significant changes at both the highest and second highest frequency tested. _Group Delay for Highest Frequency with a Present DPOAE._ In the weighted group delay examination, three out of nine patients (33%) demonstrated significant changes in group delays. Changes in group delay between baseline and the second session were not observed for Patient 6, but group delay significantly decreased by the third (final) session. Patient 7 had a significant reduction in group delay between baseline and the second and third sessions, but by the final session group delay returned to the baseline value, as shown in Figure 4 (right side, f\({}_{2}\) = 7 kHz).