In case you missed it, the "whoop" in whooping cough is explained by Hilary,
"then they start the odd cough, and after about two weeks, it starts to get strong. If you watch them, they go cough, cough, cough, cough, cough, cough, cough (and at this point are starting to go pink in the face, cough, cough, (and at this time are starting to wonder when they can have an in-breath) cough, cough, and then right at the end, they stop coughing, and the inbreath is really fast, because they want to expand their lungs."
The WHOOP is the sound made when breathing back in quickly as they try to catch their breath.
"If it takes a lab to make it, it takes a lab to digest it". Kris Carr, Hungry For Change