SonaLab - Real-Time Vocal Analysis Software
← Back to Knowledge Base

Vocal Cord Basics

What Are Vocal Cords?

Vocal cords (also called vocal folds) are two symmetrical folds of mucous membrane stretched across the larynx. When air from the lungs passes through them, the vocal cords vibrate to produce sound — this is the foundation of speech and singing.

Adult male vocal cords are approximately 17–25 mm long, while female vocal cords measure about 12.5–17.5 mm. Longer and thicker vocal cords produce a lower fundamental frequency, which is why male voices are typically deeper than female voices.

Basic Structure of the Vocal Cords

Vocal cords are not simply "two strings" but rather a sophisticated multi-layered structure:

  • Epithelium: The outermost protective barrier, composed of squamous epithelial cells
  • Superficial lamina propria (Reinke's space): A soft, gel-like tissue that is key to vocal cord vibration
  • Intermediate and deep lamina propria: Made of elastic and collagen fibers, forming the vocal ligament
  • Vocalis muscle (thyroarytenoid muscle): The innermost muscle layer that controls vocal cord tension and shape

    • Key Muscles of the Vocal Cords

    Your vocal cords rely on several important muscle groups. Understanding them helps you make sense of what happens when you sing:

  • Thyroarytenoid muscle (TA): Shortens and thickens the vocal cords, adding "firmness." Dominant in the lower range
  • Cricothyroid muscle (CT): Stretches and thins the vocal cords. Dominant in the upper range
  • Arytenoid muscles and other adductors: Responsible for bringing the two vocal cords together (closure)

    • When singing, the TA and CT muscles need to coordinate. In the low range, the TA dominates and the cords are thicker. In the high range, the CT dominates and the cords thin out. "Vocal cord firmness" is the tension produced when TA and CT work simultaneously against each other — this matters a lot for producing quality sound.

    Vocal cords are "semi-voluntary muscles" — you can't control them as precisely as your fingers, but you can gradually build better coordination through practice.

    How Is Sound Produced?

    Sound production follows the "myoelastic-aerodynamic theory":

    1. The brain sends signals to laryngeal muscles, bringing the vocal cords together (adduction)

    2. Exhaled air from the lungs builds up pressure below the glottis

    3. When air pressure exceeds the closing force of the vocal cords, they are pushed apart

    4. After the air passes through, the vocal cords snap back together due to their elasticity and the Bernoulli effect

    5. This open-close cycle repeats tens to thousands of times per second, producing the fundamental tone

    How to Protect Your Vocal Cords

    Understanding how vocal cords work helps us take better care of our voice:

  • Stay well hydrated to keep the vocal cord mucosa moist
  • Avoid prolonged loud speaking or shouting
  • Resist the urge to frequently clear your throat, as this increases vocal cord impact
  • Use diaphragmatic breathing when speaking to reduce laryngeal tension
  • If hoarseness persists for more than two weeks, seek medical evaluation promptly