What makes my child whoop?

Whooping cough: The most serious cause of a "whoop" sound in children is whooping cough, although other respiratory infections, including croup, can sometimes sound similar. Whooping cough, or pertussis, is a very serious, vaccine preventable infection. If you have any concerns about changes in your child's breathing, contact your pediatrician.

Rapid air inflow : When trying to expell heavy mucous or debris from the airways, infants can go thru a increasingly forceful effort. Shallow partial coughs are stacked on top of each other, without inward air movement until the series ends, followed by rapid inward air movement that vibrates the airways causing the whoop. Pertussis is the best known cause, but other less worrisome problems could cause similar noise.

And....: In addition to illness, a " whoop" may be heard in tracheomalacia, a benign immaturity of the trachea. Also a tic or involuntary muscle movement, vocally can be that sound.