Development of quantitative evaluation system of hypernasality

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Hypernasality attributable to abnormal resonance is one of the most frequent, severe speech disorders in the patients with cleft palate or maxillary resection. The objective evaluation of hypernasality has not been established, resulting in impairment in the diagnosis and treatment. This study was carried out to develop an objective, quantitative method for evaluating nasal resonance, in particular, hypernasality. Following results were obtained.1.After repetition of improvement for equipments, an voice analyzing system was developed. The system immediately displayd one-third octave spectra which were obtained from acoustical processing of band-pass filtered speech samples.2.Nasal resonance was acoustically assessed by this system in cleft palate patients, maxillectomy patients and normal subjects. Analysis of one-third octave spectra revealed an increase in power level between the first and second formants, and a reduction in power level in second and third regions among utterances judged to be hypernasal.3.Multiple regression analysis revealed a high correlation between the perceived severity of hypernasality by well-experienced speech pathologists and quantitative evaluation obtained by this system. This result indicated usefulness of the system.