Further Evaluation of a Hearing Loss Simulator

A real-time, level-expansion system to simulate hearing loss for normal hearing persons was studied. The simulator's effect on the performance of normal hearing subjects in basic psychoacoustic tasks was investigated through experimentation. The experiments performed included measurements of intensity discrimination, critical ratio, and two-tone suppression. The results of these experiments were predicted by analyzing a model of the simulator system. The results of a psychophysical tuning curve (PTC) experiment were also predicted and compared with previous data. In addition to the expansion simulation, an additive noise based simulation of hearing loss (equivalent threshold masking) was investigated in each experiment. Results show that the noise and expansion simulations produce comparable effects that are similar to the effects of a real impairment in the PTC and critical ratio experiments. In the intensity discrimination experiment, the expansion simulation gave subjects abnormally good sensitivity, which is not associated with real impairment. Software meant to increase the precision and ease of use of the expansion simulator and stimulus generation equipment was written and documented. Thesis Supervisor: Louis D. B. Braida Title: Henry Ellis Warren Professor of Electrical Engineering