Transcript vocal folds
Version WS 2007/8 Speech Science Speech production II – Phonation Topics • Kinetic energy to acoustic energy • The phonatory process • Structures of the larynx Homework: a) Kent, Chap. 4, pp. 100-134 b) Borden, Harris & Raphael, Chap. 4/5, pp. 72-88/65-193 Deutsch: c) Pompino-Marschall, Teil II, 31-42 d) Reetz, Kap. 3, Teil 3.2, S. 110-128 Übung 3 (22 Nov): Looking at the glottal signal: Laryngography Homework: Exercise sheet. Kinetic to acoustic energy • The kinetic energy of the airstream must be transformed into acoustic energy; otherwise we can‘t hear anything! • This is achieved by introducing some “disturbance“ into the uniformity of the (laminar) airflow. • The “disturbance“ can either be regular or irregular. (periodic or aperiodic) • The first point at which the transformation of the airstream can occur on the way from the lungs to the outside is at the larynx, when it passes between the vocal folds (through the glottis, as the gap is called) • If the vocal folds vibrate, the result is a periodic fluctuation of the air-pressure; if they are stiff, the result is aperiodic. P + 1/2 p U2 = constant The folds vibrate … • because the vocal folds are close together • because of the airflow • and because the muscle tissue has elasticity • = aerodynamic myo-elastic theory Pressure + 1/2 density x Volume velocity2 = constant i.e., when the airflow increases in the narrowed glottis, the pressure decreases. The folds vibrate … • because the vocal folds are close together • because of the airflow • and because the muscle tissue has elasticity • = aerodynamic myo-elastic theory A mechanical model • shows the elasticity of the folds • allows the twopart movement; top and bottom • with a flexible link between top and bottom Quelle The vocal folds… • have two muscular parts: • the external (here) the internal (next) thyroarytenoid (muscle names are given after the places where the muscles are attached) The vocalis muscle… • is the internal thyroarytenoid Activating or relaxing the vocalis together with, or independent of the external thyro-arytenoid muscle …. … means that the vocal folds can have many different properties which affect the way they vibrate. The vocal folds together and apart • They have to be together (adducted) to vibrate for voiced sounds…. (and even more firmly together to stop things going down!) • …and they have to be apart (abducted) to: - let us breathe freely and - produce voiceless sounds • This mobility has nothing to do with the vocal folds themselves; it is done with the arytenoid cartilages (the posterior attachment point of the vocal folds – cf. the name of the muscles) The arytenoid cartilage movements The arytenoid cartilage movements transverse and oblique arytenoid muscles Degrees of adduction a) normal adduction (“modal voice“) b) extreme adduction (“hard/pressed voice“) c) weak adduction (“breathy voice“) The rest of the larynx • The arytenoid cartilages (with the thyro-arytenoid muscles attached) rest on the cricoid c. • The thyroid cartilage (also with the thyro-aryt. muscles attached) rests on the cricoid cartilage too, standing on two legs • This arrangement means that the thyroid c. can tip forwards and back ….. The thyroid cartilage Movement of thyroid c. relative to the cricoid c. Difference in angle of male and female thyroid c. Stretching the vocal folds The whole picture • Muscle connections between the larynx and other structures (head and thorax)