Acoustic Change Complex as an Objective Adjunct for Assessing Spectral Envelope Change Detectability Using Spectral Ripple Stimuli

Purpose: Behavioral measures of spectral envelope change detection, such as spectral ripple discrimination, are clinically informative but are influenced by attention, cognition, and task compliance. This study evaluated whether the acoustic change complex (ACC) can serve as an objective adjunct measure of spectral envelope change detectability in adults with normal hearing and examined the relationship between ACC latency measures and behavioral spectral ripple discrimination within the same cohort. Method: Fifteen adults with normal hearing (18–25 years of age) first completed behavioral spectral ripple discrimination testing to estimate perceptual thresholds, followed by ACC recordings. ACC responses were then recorded to ripple stimuli at three densities: 1 ripple per octave (RPO; low difficulty), 5 RPO (near threshold), and 8 RPO (above the spectral resolution limit). Primary electrophysiological outcomes included change-related peak latencies and amplitudes (P1′, N1′, P2′, N2′). Test–retest reliability was assessed using intraclass correlation coefficients (ICCs), and associations between behavioral thresholds and ACC measures were examined using Pearson correlations. Results: ACC responses were robust and consistently observed at 1 and 5 RPO, but no reliable ACC responses were identified at 8 RPO under the predefined detection criteria. Change-related latencies were significantly shorter for 5 RPO compared to 1 RPO ( p = .038–.039), whereas amplitude measures did not differ significantly between conditions. Test–retest reliability was good to excellent (ICC = .74–.94). Behavioral ripple discrimination thresholds were moderately correlated with ACC latency measures ( r = .52–.61, p < .05), suggesting a relationship between neural timing and the detectability of spectral envelope changes. Conclusions: ACC responses to spectral ripple transitions are associated with the detectability of spectral envelope changes and demonstrate good reliability. Latency-based ACC measures provide an objective adjunct to behavioral assessment. They may be useful for estimating the detectability of changes in spectral envelopes in populations where behavioral testing is not feasible.