Objective neural indices of speech-in-noise perception

Abstract

Numerous factors contribute to understanding speech in noisy listening environments. There is a clinical need for objective biological assessment of auditory factors that contribute to the ability to hear speech in noise, factors that are free from the demands of attention and memory. Subcortical processing of complex sounds such as speech (auditory brainstem responses to speech and other complex stimuli [cABRs]) reflects the integrity of auditory function. Because cABRs physically resemble the evoking acoustic stimulus, they can provide objective indices of the neural transcription of specific acoustic elements (e.g., temporal, spectral) important for hearing speech. As with brainstem responses to clicks and tones, cABRs are clinically viable in individual subjects. Subcortical transcription of complex sounds is also clinically viable because of its known experience-dependence and role in auditory learning. Together with other clinical measures, cABRs can inform the underlying biological nature of listening and language disorders, inform treatment strategies, and provide an objective index of therapeutic outcomes. In this article, the authors review recent studies demonstrating the role of subcortical speech encoding in successful speech-in-noise perception.

Figure 1.

Time domain of a 40-ms stimulus /da/ (gray) and response (black)

Figure 2.

Stimulus timing and responses are presented for /ba/ (blue), /da/ (red), and /ga/ (green) syllables

Figure 3.

The strength of F₀ encoding is related to Quick Speech-in-Noise test scores (QuickSIN: r_s = .523, p − .031). Similar group differences for the F₀ have been found in children with good and poor SIN perception (Anderson et al., IN PRESS). Adapted from Song et al., (IN PRESS).

Figure 4.

Effects of noise on brainstem responses in children with good and poor speech-in-noise (SIN) perceptions

Figure 5.

Grand average response waveforms of typically developing children (N = 21) in response to repetitive (red) versus variable (black) presentation of speech syllable /da/ (top panel)

Figure 6.

Years of musical practice relate to Quick Speech-in-Noise Test (QuickSIN) scores (r = −.580; p = .001) and working memory scores

Figure 7.

Comparison of brainstem responses to the speech syllable /da/ in quiet and babble noise conditions in musicians versus nonmusicians

Figure 8.

Case study demonstrating the cABRs of 2 participants with nearly identical audiograms (top left) but differing ability to hear in background noise on the Speech, Spatial, and Qualities of Hearing Scale (SSQ; 8.5/10 vs. 4/10 on four background-noise-related questions; bottom left)