Contribution of Fundamental Frequency to Perceived Vocal Roughness: Evidence From Time-Scaled Natural Voice Samples

Objectives.Fundamental frequency (f o ) influences auditory roughness in psychoacoustic paradigms; however, it remains unclear how changes in f o alone, when applied to dysphonic voices, alter perceived vocal roughness and breathiness.We investigated how roughness and breathiness change when f o is systematically manipulated in dysphonic voices while maintaining the time-domain waveform shape.Methods.Natural sustained vowels from dysphonic or nondysphonic speakers were resynthesized in Praat by time-scaling so that f o was converted from the original value to a target f o of 50, 100, or 200 Hz without altering the overall waveform shape (Experiment 1).In Experiment 2, an extended low-f o set was created by converting f o to 30-100 Hz in 10-Hz steps.Experienced raters evaluated each token for roughness and breathiness.Linear mixed-effects models tested whether changes in f o predicted perceptual ratings after accounting for within-token and between-rater variability.Receiver operating characteristic (ROC) analysis was used to identify an f o cutoff associated with higher roughness in Experiment 2. Results.Across experiments, lowering f o systematically increased roughness ratings, whereas breathiness showed comparatively smaller and less consistent changes.In mixed-effects models, f o was an independent predictor of roughness but not of breathiness.In Experiment 2, ROC analysis identified an f o threshold of 70 Hz for differentiating higher versus lower roughness.These patterns are consistent with auditory accounts in which reduced harmonic spacing relative to cochlear bandwidths enhances within-band interactions and temporal-envelope modulation.Conclusions.By manipulating f o while preserving waveform shape, we identified an auditory contribution of f o to perceived vocal roughness that is largely distinct from breathiness.These findings support the development of acoustic roughness indices that account for fo-dependent harmonic spacing and critical-band envelope modulation, and they underscore the need to consider f o when interpreting auditory-perceptual roughness ratings.