Vocal roughness and jitter characteristics of vowels produced by esophageal speakers

Audiotape recordings of sustained vowels produced by nine esophageal speakers were subjected to acoustic and perceptual analysis. Results indicated that (1) the magnitude of vocal jitter present in the vowels was substantially larger than that observed in normal speakers and speakers with laryngeal/vocal disturbance, (2) listeners could reliably rate the severity of vocal roughness in the vowels, (3) voices of esophageal speakers were characterized by varying degrees of vocal roughness, and (4) mean fundamental frequency, mean jitter, or jitter ratio measures did not serve as useful predictors of the perceived severity of vocal roughness. These findings are interpreted to suggest that the mechanism esophageal speakers employ to regulate fundamental frequency is substantially different from that employed by normal speakers and that the identity of physical variables underlying the perception of roughness severity in naturally produced human speech is not well understood.