SUBJECTIVE JUDGMENTS OF SPEECH CLARITY MEASURED BY PAIRED COMPARISONSAND CATEGORY RATING

Objective: The purpose of this study was to compare listeners' subject ive judgments of speech clarity via paired comparisons and category ra ting using stimulus conditions that varied in the relative spacing bet ween stimulus items, producing either a wide or narrow range of perfor mance. Design: Subjective judgments of speech clarity were measured vi a paired comparisons and category rating in 12 normal-hearing (Experim ent 1) and eight hearing-impaired adults (Experiment 2). Sentences pro cessed by six band-pass filters that increased monotonically in Articu lation Index (AI) estimates constituted the stimuli to be judged. Usin g subsets of three filters from the group of six, subjective judgments were additionally obtained for stimulus conditions in which the perfo rmance ranges were wide (large differences in Al) and narrow (small di fferences in AI). Results: Speech clarity judgments obtained by paired comparisons and category rating were highly related to the Al estimat es both for normal-hearing and hearing-impaired subjects. When the per formance range was wide, both methods provided similar judgments for t he normal-hearing subjects. For the hearing-impaired subjects, paired comparisons were more sensitive than category rating. When the perform ance range was narrow, paired comparisons were more sensitive than cat egory rating in differentiating between filters for both groups of sub jects. This difference was less obvious for the normal-hearing subject s when paired comparison data were converted to a scale comparable to the category ratings. Large between-subject variability was evident fo r the hearing-impaired subjects on the psychophysical scaling procedur es, most notably for category rating. Conclusions: When judging the cl arity among stimulus items where performance varied over a wide range, both category rating and paired comparisons provided comparable judgm ents for normal-hearing listeners. For conditions in which perceptual differences between stimulus items were restricted either by the choic e of conditions or by the effects of sensorineural hearing loss, the m ethod of paired comparisons was the more sensitive procedure.