Throat clearing

Throat clearing is forcibly, sometimes mutedly, expelling air from one's lungs, sometimes to clear mucus, sometimes to attract attention to something. It is less vigorous than coughing.

Cause
Throat clearing may be articulated consciously or unconsciously, and may be a symptom of a number of laryngopharyngeal (upper respiratory tract) ailments. Occasionally the cause is a common cold or post-nasal drip. The nose dispatches mucus which is meant to assist clearing infections and allergens. Mucus which is thick is forced out with a throat clearing sound. Another cause is laryngopharyngeal reflux.

Mechanism
Throat clearing is a sound made at the back of the throat. The act of clearing the throat causes the folds in the throat to vibrate similar to a cough so it may be harmful if it is continuously practiced.

Onomatopoeia
When the pressure is restricted with a closed mouth, as is common in polite society, the sound is articulated as a single-syllable exclamation, written onomatopoeiacally as "hem"; or it may be articulated as a double-syllable sound, written as "ahem", which is expressed by inhaling slightly and then exhaling more forcibly. An alternate onomatopoeia written "hock" or "hawk" (as in "to hock a loogie") represents the impolite sound of loudly expelling a bolus of sputum with an open mouth.

Paralanguage
A deliberately executed throat clearing can be a nonverbal, paralingual form of metacommunication. A loud, exaggerated throat-clearing noise may sometimes be used to get attention; as in the case of a parent signaling to a child that they should behave.