Hearing and Donuts (Brain and Bagels) Seminar
October 7 @ 8:30 am - 9:30 am
Erik Jorgensen, Au.D, Ph.D.
Communication Sciences and Disorders
University of Wisconsin
Topic: What is noise? An investigation of complexity in real-world noise and its effect on speech perception for listeners with normal hearing and hearing loss.
Difficulty hearing speech in noise is a common problem, especially for listeners with hearing loss. Hearing aids are the primary treatment for hearing loss. However, hearing aid technologies that are efficacious in laboratory tests of speech in noise perception are not effective in real-world noisy environments, leading to low rates of hearing aid use and satisfaction. The gap between laboratory efficacy and real-world effectiveness suggests that environmental factors, particularly the types of noise encountered in the real world and not accounted for in laboratory tests, contribute in critical ways to speech perception in noise and hearing aid effectiveness. The purpose of this study was to investigate how real-world noise, both within and between real-world noisy environments, affects speech perception for listeners with normal hearing and listeners with hearing loss. To meaningfully investigate how different moments and types of real-world noise affect speech perception, a metric of ‘noisiness’ had to first be applied to real-world noise. This study proposed to quantify noise via its acoustic complexity using entropy in the time and frequency domains. Then, using both laboratory and field experiments, the effects of entropy in noise on speech perception were investigated. In the laboratory experiments, entropy from 8 real-world noisy soundscapes was systematically quantified. Using a trial-by-trial design, participants repeated back sentences in an Ambisonics environment that replicated real-world soundscapes. The entropy of the real-world noise was varied and the effect on speech perception was quantified. Entropy had significant effects on speech perception, with higher entropy resulting in poorer speech perception. Effects were larger for entropy in the time domain than the frequency domain. Effects were larger for participants with normal hearing than participants with hearing loss, and larger for participants with hearing loss in the aided than unaided condition. For the real-world experiments, participants wore an open master hearing aid that recorded noisy environments encountered in daily life by participants. Participants then completed ecological momentary assessments to report on their listening experiences in those environments. The effects of entropy in the real-world were more equivocal, but generally mirrored the findings of the laboratory experiments, with clearer effects of entropy in the time domain than frequency domain, for participants with normal hearing than hearing loss, and for participants with hearing loss in the aided than unaided condition. For speech listening, greater time-domain entropy generally yielded greater listening effort and higher perceived complexity for speech listening. Greater frequency-domain entropy yielded greater listening effort for participants with hearing loss in the aided condition. The findings from this study shed light on why traditional laboratory tests of speech in noise perception may not reflect real-world listening. Further, the results reveal important considerations for future investigations using virtual sound environments in the lab and ecological momentary assessment in noisy environments in the real world.