Figure 3: ECochG results from noise exposed dental technicians. Left panel shows ECochG responses recorded from the right ears of Patient 3 (top), Patient 4 (middle) and, and Patient 5 (bottom), and right panel shows ECochG responses recorded from the left ears of Patient 3 (top), Patient 4 (middle), and Patient 5 (bottom). The recordings were from tympanic membrane to click presented in alternating polarity at 100 dB nHL. For Patient 1, the ratios of the summating potentials (SP) and action potential (AP) amplitudes (<0.4), and areas (<1.5) were normal. In contrast, Patient 4 showed abnormal high SP/AP amplitude and area ratios in the left ear (0.9, 5.1, respectively) while the contralateral ear demonstrates normal SP/ AP amplitude and area ratios. Both ears of Patient 5 were reported to have abnormal SP/AP amplitude (>0.4) and area (>1.5) ratios. All measurements were made with a reference of base line (BL). ECochG traces from Patients 1 and 2 were normal but not included.