발성시 성대 주위의 유동 특성 및 음향장 예측 = Prediction of Flow Characteristics and Aeroacoustic Fields around the Vocal Folds during Phonation

다국어 초록 (Multilingual Abstract)

Numerical investigation of unsteady airflow and acoustic fields around the vocal folds is performed to understand the sound generation mechanisms and characteristics during phonation. The idealized geometry of the human glottis is oscillated with a fundamental frequency to replicate the self-sustained vocal folds motion due to the pressure difference between the supraglottal and subglottal regions. The flow in the vocal tract is modeled as an incompressible, two-dimensional, axisymmetric form of the Navier-Stokes equation, since the Mach number is less than 0.1 within the glottis. The acoustic field is predicted by using a new hydrodynamic/acoustic splitting method with a high order accurate compact finite difference method. Computational results show that a pulsating jet is formed by the vocal folds motions and the dominant sound source is dipole-type pressure fluctuations around the glottis wall. The computed glottal volume velocities agree well with the inverse filtered data by Rothenberg for two cases of various subglottal pressure and fundamental frequencies. The rotational (converging-diverging) component of the glottis motions is found to have significant influences on the glottal impedance and accelerate the opening and closing movement of the vocal folds.

목차 (Table of Contents)

• Abstract i
• 목차 iii
• List of Figures v
• List of Table vii
• 기호 설명 viii
• 제 1 장 서 론 1
• 1-1. 연구 배경 1
• 1-2. 연구 사례 4
• 1-3. 연구 목적 6
• 제 2 장 공력음향 전산해석 기법 8
• 2-1. 유동 음향 분리 기법 8
• 2-1-1. 비압축성 지배방정식 10
• 2-1-2. 압축성 요동 방정식 11
• 2-2. 수치해석 기법 13
• 2-2-1. 컴팩 유한 차분법 13
• 2-2-2. 좌표 변환 15
• 2-2-3. 공간 필터링 19
• 2-3. 경계 조건 21
• 2-3-1. 이동 벽면 조건 21
• 2-3-2. 비반사 경계 조건 22
• 제 3 장 수치해석 기법 검증 24
• 제 4 장 공력 음향 예측 29
• 4-1. 성대 형상 및 유동 조건 29
• 4-2. 격자 생성 32
• 4-3. 맥동성 제트 35
• 4-4. 음성 원음 38
• 4-5. 성문 하압 41
• 4-6. 회전 운동과 기본 주파수 45
• 제 5 장 결론 및 향후 연구 과제 51
• 참고 문헌 53