In order to evaluate the relationship between hearing loss and effect of residual hearing upon speechreading, and to examine the relationship between informations conveyed visually and auditory, Japanese syllabic articulation scores and confusion matrices were measured under three conditions : visual and auditory reception (alone and combined). As the subjects of this experiment were required to have learned syllables, seven students of a high school for the deaf and six pupils of the upper grade in a hard-of-hearing class in an elementary school were selected, referring to their audiograms (Table 1). Materials used were four sets of 30 syllables consisting of frequently used Japanese syllables and bilabial syllables that serve as cue to speechreading. These syllables were spoken in random order by an adult female and were recorded on videotape. The materials were presented to subjects over a 10 inches black-and-white video monitor placed at 1. 5meters from the subjects under the following three conditions: (1) image only: visual reception, V, (2) speech only: auditory reception, A, and (3) both image and speech: visual-auditory reception, V+A. Syllabic articulation scores obtained under V+A, V, and A conditions are represented (V+A), (V), and (A), respectively, and relations between them and hearing loss are shown in Figs. 1, 2, and 3. (V+A) ranges from 20% to 80%, and decreases with increase of hearing loss. (V) ranges below 40% but shows no apparent relation with hearing loss. On the other hand, (A) ranges below 60% and, similarly to (V+A), decreases with increase of hearing loss. Then, (V+A)-(V) is defined as "effect of residual hearing upon speechreading" and the relationship between this and hearing loss is shown in Fig. 4. It was found in this figure that the effect of residual hearing upon speechreading was inversely related to hearing loss in dB. The effect was more noticable among the pupils attending a hard-of-hearing class. Table 2 shows coufusion matrices among five Japanese vowels obtained under the three conditions: V, A, and V+A. The figure below 4% has been cut off to make it more clear. In case of visual reception, some errors were made near the diagonal. In the case of auditory reception, on the other hand, significant errors were made on the other diagonal. Vowels were recognized fairly well by visual reception, but the percentage of correct response by visual-auditory reception was increased still more. Fig. 5 shows the consonants obtaining the percentage of correct response over 45% under the three conditions: V, A, and V+A. Three phonemes /w, r, m/ were recognized by visual reception and two phonemes /m, k/ by auditory reception. In addition to these four phonemes, 5 more phonemes /p, t, n, h, j/ were recognized by visual-auditory reception. These phonemes were unrecognizable by visual and auditory reception alone but were recognized by combining the two. No other phonemes reached 45% level under any condition. From confusion matrices among vowels and among consonants under the three conditions, the percentage of correct response classified by manner of articulation and place of articulation was calculated and shown in Fig. 6. Visual reception is effective in distinguishing place of articulation and auditory reception is effective in distinguishing manner of articulation, and visual cues and auditory cues complement each other.
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