The impact of "hidden" hearing loss, reduced inhibition of cognitive interference, and aging on behavioral adaptation to noise

Abstract

[EN] Understanding speech in noisy environments is challenging but essential for human verbal communication. Fortunately, the auditory system can adapt to background noise, which facilitates speech intelligibility in noisy environments. Behavioral adaptation to noise, however, varies across individuals for reasons that are unclear. The aim of the work presented in this thesis was to investigate whether behavioral adaptation to noise is affected by ‘hidden’ hearing loss (HHL), a reduced ability to inhibit cognitive interference, or aging. Eighty-nine adult speakers of Castilian Spanish (19–86 years old) with clinically normal hearing participated in the experiments. Speech reception thresholds (SRTs), the signal-to-noise ratio at 50 % recognition, were measured for disyllabic words embedded in noise. SRTs were measured for words delayed 50 ms and 800 ms in the noise, for various noises and levels. Adaptation to noise was calculated as the improvement in the long-delay relative to the short-delay condition. Because adaptation is greater for vocoded than for natural words, words were processed through a tone vocoder. The risk of HHL was assessed using the amplitude and the rate of growth (slope) of wave I of the auditory brainstem response (ABR). The ability to inhibit cognitive interference was assessed using the Stroop color and word test. The data revealed that participants exhibited significant adaptation to noise, and that adaptation was greater at higher noise levels and for steady than for fluctuating noises. However, adaptation was not significantly associated with ABR wave I amplitude or slope, age, or Stroop test score, even after controlling for the potential confounding effect of audiometric threshold. Findings suggest that behavioral adaptation to noise is preserved across the adult lifespan and is independent of subclinical auditory deficits or inhibitory control abilities. Findings further suggest that speech-in-noise difficulties experienced by older adults or individuals at risk of suffering from HHL should be attributed to factors other than impaired adaptation to noise.