Coughing is a sudden expulsion of air from the lungs through the epiglottis, cartilage located in the throat, at an amazingly fast speed. Compared to a tennis ball hit at 50 miles per hour, or a baseball at 85 miles per hour...coughing is faster, with an estimated speed of 100 miles per hour. With such a strong force of air, coughing is the body's mechanism for clearing the breathing passageways of unwanted irritants.
Let's take a look at the vocal cords prior to a cough.
In order for a cough to occur, several events need to take place in sequence. Let's use the unwanted irritant of water entering the windpipe, also known the trachea, to trigger the coughing reflex.
First, the vocal cords open widely allowing additional air to pass through into the lungs. Then the epiglottis closes off the windpipe, and simultaneously, the abdominal and rib muscles contract, increasing the pressure behind the epiglottis. With the increased pressure, the air is forcefully expelled, and creates a rushing sound as it moves very quickly past the vocal cords. The rushing air dislodges the irritant making it possible to breathe comfortably again.