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The vocal quality of a patient is modeled by means of a Dysphonia Severity Index (DSI), which is designed to establish an objective and quantitative correlate of the perceived vocal quality. The DSI is based on the weighted combination of the following selected set of voice measurements: highest frequency (F0-High in Hz), lowest intensity (I-Low in dB), maximum phonation time (MPT in s), and jitter (%). The DSI is derived from a multivariate analysis of 387 subjects with the goal of describing, purely based on objective measures, the perceived voice quality. It is constructed as DSI = 0.13 x MPT + 0.0053 x FO-High - 0.26 x I-Low - 1.18 x Jitter (%) + 12.4. The DSI for perceptually normal voices equals +5 and for severely dysphonic voices -5. The more negative the patients index, the worse is his or her vocal quality. As such, the DSI is especially useful to evaluate therapeutic evolution of dysphonic patients. Additionally, there is a high correlation between the DSI and the Voice Handicap Index score.
KEY WORDS: voice quality, voice assessment, acoustic, voice range profile, index
Vocal performance has increasingly gained interest in our society, which is evolving into a service-oriented community. This growing interest has consequently induced a lot of multidisciplinary research concerning voice assessment and therapy with a comprehensive battery of tests focusing on qualitative and quantitative aspects of vocal performance.
The medical diagnosis of vocal fold pathology is mainly based on an endoscopic exam of the vocal folds and upper airway tract. Voice dysfunction on the other hand is assessed by perceptual judgment and objective measures, such as acoustic and aerodynamic characteristics. However, perceptual evaluation is one of the most controversial topics in voice research. Review of literature reveals a wide variety of rating scales (Gelfer, 1988; Hammarberg, 1992; Hirano, 1981; Laver, 1980; Wendler, Rauhut, & Kruger, 1986; Wilson, 1987; Wirz & Mackenzie Beck, 1995) and reliability data fluctuating from study to study (Bassich & Ludlow, 1986; Blaustein & Bar, 1983; Kreiman, Gerratt, & Berke, 1994; Kreiman, Gerratt, Kempster, Erman, & Berke, 1993). So far, there is no internationally accepted perceptual judgment protocol, but the GRBAS scale (Grade of hoarseness, R for roughness, B for breathiness, A for astheny, and S for strain) proposed...