This research will be done in collaboration with Drs. Denise Menezes and Silvana Griz at the Universidade Federal de Pernambuco ('Federal University of Pernambuco') in Recife, Brazil, as an extension of NIH Grant No. R01DC001507, 9-20-2008 to 8-31-2013. Listeners with normal hearing usually find speech recognition easier in a modulated background than in a steady background that has the same overall level. This modulation benefit - or masking release - is typically more pronounced in younger listeners than older listeners. The purpose of this project is to assess the contribution of central deficits in temporal processing to this age-related reduction in masking release.
Specific Aim 1 examines the relationship between speech recognition in modulated noise and temporal masking performance as a function of age, controlling for audibility. Masking release for both American English and Brazilian Portuguese will be measured. The goal is to assess the extent to which forward and backward masking by the masker peaks obscures speech information in the masker troughs, thereby limiting modulation benefit. The issue of age effects in forward masking is itself undeveloped, and findings are mixed as to whether older listeners exhibit exacerbated forward masking. The purpose of Specific Aim 2 is to relate psychophysical and electrophysiological measures of forward masking as a function of age in order to clarify this issue. The focus on masking effects will specifically employ speech-relevant stimuli. Jointly, these two interwoven aims will advance our understanding of how the normal aging process compromises temporal masking - particularly as it relates to speech recognition in fluctuating backgrounds. This understanding will be 'globalized'by undertaking the investigation simultaneously in two countries (U.S. and Brazil) using two languages (American English and Brazilian Portuguese).
The global burden of compromised communication associated with age-related hearing loss is enormous and represents a major public health challenge. This project investigates one facet of age- related hearing difficulty which is the reduced benefit exhibited by older listeners for hearing speech in an interrupted background. Understanding the role that temporal processing deficits plays in this reduced masking release will contribute to the scientific knowledge base that can address - and potentially alleviate - this public health challenge.!