목적: The voice and speech alternations after total thyroidectomy are usually due to the recurrent or superior laryngeal nerve injury. However, these alterations may also be associated with other extralaryngeal factors, such as neck muscle dysfunction and scar contracture of the neck. We evaluated the acoustic characteristics of oral vowels and the changes of hyoid bone movement before and after thyroidecotmy. 방법:Patients aged 19 to 58 years undergoing total thyroidectomy, in the absence of laryngeal/pulmonary disease, previous neck surgery, or other malignant diseases, were subjected. For the acoustic analysis of oral vowels, the fundamental frequencies(Fo) and vowel space areas were evaluated before surgery, at 7 days, and 3 months after surgery. For the hyoid bone movements, the videofluoroscopic images were used at the same periods. 결과:The Fo level significantly decreased after the surgery in the following seven vowels. Regarding the vowel formant changes, the F1 of vowel /e/ significantly decreased at 3 months post-operatively from the baseline, and the F3 of vowel /i/ significantly decreased at 7 days post-operatively from the baseline. No statistically significant change in the vowel space area was observed. On the change in the hyoid movements, the Y coordinate of vowels /i/ and /e/ significantly decreased at 7 days post-operatively from the baseline. 결론:In this study, changes in the fundamental frequency, formant, vowel space area, and hyoid bone position after the surgery were compared using the following oral vowels. The quantitative results of this study may be used as basic data on voice disturbances for voice management in thyroidectomy patients.