When speaking, air moves through folds in the larynx and this produces sound vibrations. If swelling or obstruction occurs within the vocal cords, the vibration is altered. The most common cause of loss of voice is infection and inflammation of the larynx leading to swelling of the vocal folds. . Misuse and overuse of the voice can cause the vocal folds to swell and become unable to vibrate as needed for speech, it is another common cause of voice problems. Loss of voice may also occur with any infection of the upper respiratory tract or with serious allergic reactions, such as anaphylaxis. The inability to produce voice can also happens when the person suffers a major traumatic event which leads to the state of shock.
Aphonia is different from aphasia, which is a language disorder. Aphonia is more severe than dysphonia, the medical term for a vocal disorder, of which laryngitis (inflammation of the larynx) is one cause.