Owing to the development of medical technology, devices to assess resonance (hypernasality and hyponasality) which result from conditions such as cleft palate and brain injury are being studied. In general, nasometric instruments are used to support clinical judgments of these disorders. For conventional separation-type nasometric instruments, there is an acoustic feedback effect between oral and nasal sounds. Recently, a mask-type nasometric instrument was developed for acoustic feedback insensitivity, but it has not yet been popularized. In this study, we analyzed the acoustic characteristics of the mask-type structure according to existing nasometric instruments. We evaluated the acoustic collection characteristics of the structure through the lumped-element model with an electromechanical-equivalent circuit. The analysis confirmed that the optimum area of the acoustic hole was obtained and a closed-type mask structure could be designed. In addition, we obtained voice data from a healthy control group and examined significant differences in the structure of the separation-type and mask-type nasometric instruments. Consequently, we confirmed a significant difference in nasalance according to the acoustic collection structure of the nasometric instruments.
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