What primarily governs the vibration of the vocal folds?

The vibration of the vocal folds is primarily governed by their position and the activity of the muscles that control them. When air from the lungs is pushed through the closed vocal folds, the pressure builds up until it forces them apart briefly, allowing air to escape. The elasticity of the vocal folds, combined with their tension and length, determines the pitch and quality of the sound produced.

Muscles such as the cricothyroid and thyroarytenoid play crucial roles in adjusting the tension and position of the vocal folds, which directly influences their vibratory characteristics. For example, tightening the folds increases pitch, while loosening them lowers pitch. The ability to finely adjust these muscles allows for a wide range of vocal sounds and is fundamental to speech production.

The other options touch upon aspects related to sound production but do not focus on the primary mechanism that drives vocal fold vibration. Speed of airflow is a factor in sound intensity and can influence vocal fold behavior, but it is not the main determinant of vibration. The nature of external sound stimuli can affect how the vocal tract resonates but does not govern the intrinsic properties of vocal fold vibration themselves. Surface tension of arytenoid cartilages is not directly applicable to the vibratory action of the vocal folds;