A cough is sudden and often repeated spasmodic contraction of the human chest cavity which results in the violent expulsion of air from the lungs, usually accompanied  by a distinctive sound. A cough is usually triggered to remove an accumulation of mucous secretions from the airways: the air may reach a speed of 480 km/h during passage through the airways when coughing. A cough may also be induced by a food bolus entering the trachea instead of the oesophagus due to epiglottal deficiency.