the role of the larynx in speech

Lecture No 3
Title: The role of the larynx in speech
The first point where the airflow from the lunges encounters a controlled resistance is at the larynx, which can be defined as a structure of muscles and cartilage located at the upper end of the trachea( windpipe). The resistance can be controlled by the different positions and tensions in the vocal cordswhich can be reffered to as two bands of elastic tissue situated in the larynx. During quiet breathing the cords are relaxed and spread apart to allow the free flow of air to and from the lungs. During swallowing the cords are drawn tightly together to keep foreign material from entering the lungs. For speech the most important featureof the vocal cords is that they can be made to vibrate if the airflow between them is sufficiently rapid and if they have the proper tension and proximity to each o9ther. The rapid vibration is called voicing. The frequencyof vibration determines the received pitch.
Voicing is the extra noisethat accompanies the production of the z- sound version of the plural morpheme. It is said that the z- sound is voiced, whereas the s- sound is voiceless. The lack of voicing in /s/ is due to the fact that the vocal cordsare more spread apartand tenser than during the production of /z/.