Equally intelligible, unequally robust: Effects of noise on types of dysarthric speech signals

This study investigated whether different types of dysarthric speech (with comparable baseline intelligibility) are equally susceptible to background noise. Using intrinsically degraded speech from four individuals with dysarthria, each representing a distinct motor speech disorder subtype, we examined how intelligibility is impacted by masker type (stationary vs fluctuating noise) and signal-to-noise ratio (SNR). Ninety-five listeners completed a listening task with stationary speech-shaped noise or ecologically valid cafeteria noise, across multiple SNRs. Although all degraded signals showed intelligibility declines in noise, the extent and pattern of decline varied, suggesting that not all forms of pathological degradation interact with background noise in the same way. Notably, the typical intelligibility benefit associated with fluctuating maskers (i.e., masking release) was absent for all dysarthric signals. These findings reveal that equivalently intelligible but qualitatively different dysarthric signals do not respond uniformly to environmental challenges. The results have implications for models of speech perception, which must account for complex interactions between intrinsic (speaker-specific) and external (environmental) degradations, as well as for real-world communication and intervention strategies.