LAUSR

Temporal modulations are an important part of speech signals. An accurate perception of these time-varying qualities of sound is necessary for successful communication. The current study investigates the relationship between sustained envelope encoding and speech-in-noise perception in a cohort of normal-hearing younger (ages 18-30, N = 22) and older (ages 55-90+, N = 35) adults using the subcortical auditory steady-state response (ASSR). ASSRs were measured in response to the envelope of 400 ms amplitude-modulated (AM) tones with 3000 Hz carrier frequencies and 80 Hz modulation frequencies. AM tones had modulation depths of 0 dB, -4 dB, and -8 dB relative to m = 1 (m = 1, .631, and .398, respectively). The robustness, strength at modulation frequency, and synchrony of subcortical envelope encoding was quantified via time-domain correlations, spectral amplitude, and phase-locking value, respectively. Speech-in-noise ability was quantified via the QuickSIN test in the 0 and 5 dB SNR conditions. All ASSR metrics increased with increasing modulation depth and there were no age group effects. ASSR metrics in response to shallow modulation depths predicted 0 dB speech scores. Results demonstrate that sustained amplitude envelope processing in the brainstem relates to speech-in-noise abilities, but primarily in difficult listening conditions at low signal-to-noise ratios. These findings furthermore highlight the utility of shallow modulation depths for studying temporal processing. The absence of age effects in these data demonstrate that individual differences in the robustness, strength, and specificity of subcortical envelope processing, and not age, predict speech-in-noise performance in the most difficult listening conditions.