At the top of the trachea is the voice box (larynx), which contains the vocal cords and is primarily responsible for producing the sound of the voice. When relaxed, the vocal cords form a V-shaped opening that air can pass through freely. When contracted, they vibrate as air from the lungs passes over them, generating sounds that can be modified by the tongue, nose, and mouth to produce speech.
The epiglottis is a stiff flap of cartilage located above and in front of the larynx. During swallowing, the epiglottis covers the opening to the larynx to prevent food and fluids from entering the trachea. Thus, the epiglottis protects the lungs.