Direct magnitude estimation and interval scaling of naturalness and severity in tracheoesophageal (TE) speakers

The purpose of this study was to determine the Psychophysical character and validity of auditory-perceptual ratings of naturalness and overall severity for tracheoesophageal (TE) speech. This was achieved through use of direct magnitude estimation (DME) and equal-appearing interval (EAI) scaling procedures. I Twenty adult listeners judged speech naturalness and overall severity from connected speech samples produced by 20 adult male TE speakers. A comparison of DME- and EAI-scaled judgments yielded a metathetic continuum for naturalness and a prothetic continuum for overall severity. These data provide support for the use of either DME or EAI scales in auditory-perceptual ratings of naturalness, but they provide support only for DME scales in judging overall severity for TE speech. The present results suggest that the nature of perceptual phenomena (prothetic vs. metathetic) for TE speakers is consistent with findings for the same dimensions produced by normal laryngeal speakers. These data also support a need for further study of perceptual dimensions associated with TE voice and speech in order to avoid the inappropriate and invalid use of EAI scales frequently found in diagnosis, assessment, and evaluation of this clinical population.