They were testing the myth that a duck's voice doesn't echo. A sound expert attached a voice-meter thing to the duck, and asked Jamie to make the duck quack. after several unsuccesful attempts, he told the duck:
"Quack, damn you."
(and if you meant why is it in the thread, I don't know.)
"Quack, damn you."
(and if you meant why is it in the thread, I don't know.)