Supra-threshold deficits in normal hearing military recruits exposed to impulse noise.

The aim of this study was to determine the effect of impulse noise exposure on various proxy measures of cochlear synaptopathy in young military recruits. A total of 27 military recruits with exposure to firearm and artillery noise and 13 non exposed participants were recruited. All presented with normal hearing thresholds and the presence of distortion product otoacoustic emissions (DPOAEs). The Noise Exposure Structured Interview (NESI) was used to quantify noise exposure. Speech perception in noise (SPiN), equivalent rectangular bandwidth (ERB) of auditory filters, auditory brainstem response wave I amplitude, wave I amplitude growth function, wave I/V amplitude ratio, wave V latency, wave V latency shift with ipsilateral noise, and the summating potential/action potential ratio of the electrocochleography were measured. In military participants, SPiN was worse, ERB at 4 kHz was larger, wave I amplitude at 75 dBnHL was reduced, and wave V latency was delayed. However, no significant correlations were observed between NESI and auditory measures, once multiplicity of tests was controlled for. These results suggest that military recruits may exhibit supra-threshold deficits, despite presenting with normal hearing thresholds and presence of DPOAEs. Future studies should include a measure of auditory filters in their test battery.

The Effort Required to Comprehend a Short Documentary in Noise: A Comparison of Younger and Older Francophones.

Speech processing is more effortful under difficult listening conditions. Using a dual-task paradigm, it has been shown that older adults deploy more listening effort than younger adults when performing a speech recognition task in noise. Purpose The primary purpose of this study was to investigate whether a dual-task paradigm could be used to investigate differences in listening effort for an audiovisual speech comprehension task. If so, it was predicted that older adults would expend more listening effort than younger adults. Method Three groups of participants took part in the investigation: (a) young normal-hearing adults, (b) young normal-hearing adults listening to the speech material low-pass filtered above 3 kHz, and (c) older adults with age-related normal hearing sensitivity or better. A dual-task paradigm was used to measure listening effort. The primary task consisted of comprehending a short documentary presented at 63 dBA in a background noise that consisted of a 4-talker speech babble presented at 69 dBA. The participants had to answer a set of 15 questions related to the content of the documentary. The secondary task was a tactile detection task presented at a random time interval, over a 12-min period (approximately 8 stimuli/min). Each task was performed separately and concurrently. Results The younger participants who performed the listening task under the low-pass filtered condition displayed significantly more listening effort than the 2 other groups of participants. Conclusion First, the study confirmed that the dual-task paradigm used in this study was sufficiently sensitive to reveal significant differences in listening effort for a speech comprehension task across 3 groups of participants. Contrary to our prediction, it was the group of young normal-hearing participants who listened to the documentaries under the low-pass filtered condition that displayed significantly more listening effort than the other 2 groups of listeners.