Abstract
A practical method for the qualitative analysis of impaired speech perception was developed based on graphical representations of psychoacoustic proximity among monosyllables. The psychoacoustic proximity was defined as the degree of ease of confusion among monosyllables for normal ears, and was measured as a confusion matrix among 67 Japanese monosyllables called “chokuon.” This matrix was constructed from hearing tests on unclear perception induced by lowering stimulus levels for 26 listeners with normal hearing. Configuration graphs of the monosyllables where the proximity values were represented by the mutual distances were made from the confusion matrix using a non-metric multi-dimensional scaling method known as SMACOF. Using these graphs, the perceptual failures for the monosyllables on the part of a patient can be simply documented by connecting confused stimuli and corresponding wrong responses. This documentation indicates the abnormality of a patient's failures in terms of discrepancies from the ease of confusion for normal ears. Using two hearing-impaired patients, it was concluded that the analysis of these discrepancies together with the patients' pure tone audiogram provides useful information to know how and why patients fail to perceive certain speech sounds.
