Dissertations, Theses, and Capstone Projects
Date of Degree
6-2025
Document Type
Dissertation
Degree Name
Ph.D.
Program
Speech-Language-Hearing Sciences
Advisor
Brett A. Martin
Committee Members
John P. Preece
Michelle MacRoy-Higgins
Valerie L. Shafer
Subject Categories
Social and Behavioral Sciences
Keywords
Aging, age-related hearing loss, listening effort, speech perception, event-related potentials, N400, late positivity
Abstract
Background: Older listeners often have difficulty with speech perception, particularly in background noise This difficulty may be driven by numerous variables, including aging, age-related hearing loss, and a decline in higher-level cognitive processing. This difficulty with speech perception leads to the need for listeners to use a great deal of effort when listening to speech. The overall aim was to examine the effects of speech rate and target word intensity on speech perception (measured behaviorally), speech processing (measured using event-related potentials) and listening effort (measured using subjective questionnaires as well as a dual-task paradigm) in older adults and older adults with hearing loss.
Methods: Thirteen younger adults (mean age: 28.60 years, SD: 3.84) and 19 older adults (mean age: 67.28 years, SD: 4.92) participated. The younger participants had normal hearing sensitivity between 250 Hz and 8000 Hz. Three older participants had normal hearing sensitivity at all frequencies, whereas 16 older participants had normal hearing sensitivity up to 1000 Hz with a mild- to moderate-hearing loss in higher frequencies (2000, 4000, and 8000 Hz). All older participants passed the Mini-Mental State Examination (MMSE) cognitive screening test. Conversations focused on three different topics (food, animals, locations) were presented at 65 dB SPL in a background of restaurant noise at 0 Signal-to Noise Ratio (SNR) for the baseline condition. Each conversation contained target words with high or low expectancy. A slow condition was presented using 50% time-expansion. An intensity enhanced condition was presented with higher increased target word intensity by 6 dB SPL. A dual-task paradigm was used to measure listening effort and perceived effort was evaluated using the NASA Task Load Index. Event-related potentials were recorded simultaneously with the dual-task paradigm and P3 and N400 were obtained.
Results: Analyses using linear mixed-effects models in the button-press task showed that the enhanced condition exhibited higher accuracy and faster response times for low-expectancy words compared to the slow condition and high-expectancy targets. However, the slow condition used in this study did not deliver the same benefits, exhibiting lower accuracy and longer response times for low-expectancy words compared to the enhanced condition. Regarding the NASA-Task Load Index, older adults reported requiring more listening effort compared to younger adults. Additonally, the slow condition demanded increased listening effort to recognize speech in background noise compared to the enhanced condition. In the ERP data, the negativity around 400 ms and the late positivity were more robust in younger adults in the enhanced condition than in older adults. Younger participants showed greater negativity for low-expectancy words in both slow and enhanced conditions compared to high-expectancy words, consistent with an N400 effect. In contrast, older adults demonstrated increased negativity around 400 ms for high-expectancy words in the slow condition. Within the older group, as age increased, responses between 300-500 ms were more increased in the slow condition. Additionally, as hearing loss increased, greater negativity for high-expectancy words was observed in the enhanced condition compared to the slow condition. In terms of latency, in the subtracted waves from low- to high-expectancy words, the younger group showed an earlier negativity peak latency (400-450ms) than the older group (550-600ms). However, the negativity peak latency did not show statistically significant difference across conditions within the older group. For the late positivity, the younger group exhibited a larger response in the enhanced condition compared to the older group. The late positivity for high-expectancy words was greater in the original condition compared to the slow and enhanced conditions, indicating that the enhancements did not improve late positivity for high-exxpectancy targets compared to the original condition. Within the older group, the effects of age and hearing loss were significant. As age increased, late positivity was larger for high-expectancy words in the enhanced condition compared to the slow condition. For low-expectancy words, late positivity was greatest in the original condition, followed by the slow and enhanced conditions, confirming that the enhanced condition did not increase late positivity for low-expectancy words. Similarly, as hearing loss increased, the late positivity increased for high-expectancy words in the enhanced condition compared to the slow condition, while it decreased in the original condition.
Conclusion: Increasing the intensity of target word improves speech perception and processing, particularly for low expectancy words; however, slowing the rate of speech does not confer the same benefits, at least for the stimuli used in this study. These objective findings were accompanied by perceived drops in listening effort in older adults and in the slow condition. Age and hearing loss were pivotal factors influencing speech perception, processing, and listening effort in both younger and older groups.
Recommended Citation
Chun, Hyungi, "The Impact of Speech Rate and Target Word Intensity on Speech Processing and Listening Effort in Background Noise in Older Listeners" (2025). CUNY Academic Works.
https://academicworks.cuny.edu/gc_etds/6215
