Usage examples for Quacking:

• He felt almost relieved when the remainder of the flock, taking tardy alarm from the commotion of the slowly drowning bodies, drew themselves up with tense outstretched necks, and sidled away from the scene of danger, quacking a deep note of disquietude as they went. "The Chronicles of Clovis" – Saki

• The lady lifted the gate, Mrs. Duck drew out her head and went quacking away, while Mr. Drake testified his delight and gratitude by flapping his wings and quacking at the top of his voice. "Round-about Rambles in Lands of Fact and Fancy" – Frank Richard Stockton