Amplitude ratio is simply marked with the baseline, the summating potential and the action potential. A ratio between the BSL/SP and BSL/AP is calculated automatically by the system.
PBSL=Baseline, SP= Summating Potential, AP=Action Potential, BLst=start of baseline, Blend=end of baseline, AP1=start of AP, AP2=end of AP
Area Ratio is marked by first marking the start of the baseline (BLst). The BL end will be marked automatically at the next point in the waveform where the amplitude crosses this baseline. If the waveform does not allow this, you can place the BL end manually. Now mark the SP and the AP1. (the beginning of the AP). Next mark the AP peak. Finally mark the AP2, which is where the AP ends and “changes direction”. A ratio is calculated automatically by the system.
Abnormal SP/AP amplitudes are exceeding a ratio of 0.53 as the critical value. Abnormal SP/AP area ratios are exceeding a ratio of 1.94 as the critical value (Devaiah et al., 2009).
Devaiah, A.K., Dawson, K.L., Ferraro, J.A., & Ator, G.A. (2003). Utility of area curve ratio electrocochleography in early meniere disease. Arch Otolaryngol Head Neck Surg, 129, 547-551.