The long-term aim of this project is to investigate the role of reduced frequency resolution on speech perception in complex noise for hearing-impaired listeners. The specific objective of the proposed project is to psychophysically and computationally assess speech reception in the presence of a masker that fluctuates both in time and frequency, like naturally occurring sounds. The proposed experiments are designed to compare hearing-impaired and normal-hearing listeners on a task which has been shown to highlight the effect of spread of masking (SM). By separating alternating stimulus bands to opposite ears, thus removing the effect of SM from neighboring frequency bands, initial data in normal-hearing listeners show release from masking on the order of 5 to 8 dB.
Aim 1 will test normal-hearing and hearing-impaired listeners on consonant recognition in the presence of an asynchronously modulated noise. The study will test the primary hypotheses that SM reduces available glimpsing opportunities for hearing-impaired listeners, and that removing SM enhances performance relative to normal-hearing listeners.
Aim 2 will test consonant recognition in the same conditions as Aim 1, testing normal-hearing listeners with simulated hearing-losses. The study will test the primary hypothesis that reduced audibility alone cannot explain the dichotic listening benefit in hearing-impaired listeners, but rather that reduced frequency resolution is responsible for the benefit of removing SM.
Aim 3 will computationally model the behavioral data using a modified glimpsing model. The study will test the hypotheses that spectral resolution plays a key role in asynchronous glimpsing for both normal-hearing and hearing-impaired listeners;by analyzing dichotically presented stimuli, the model is expected to predict the benefit seen in the behavioral data. Results will contribute to a better understanding of factors responsible for hearing-impaired listeners'reduced ability to follow speech in complex backgrounds, with implications for the future of auditory prosthesis design. The training program outlined in the current proposal provides strong mentorship in research design, especially with regard to signal processing, data analysis, and computational modeling.
The proposed work is relevant to the public health in that it investigates the effects of sensorineural hearing loss on the ability to process speech in the presence of competing noise. Speech testing and modeling approaches will be used to determine whether negative effects of background noise in hearing-impaired patients can be ameliorated using stimulus techniques that distribute sounds between the two ears. The results will advance our understanding of hearing-impairment and the potential for benefit via stimulus processing.