He's stopped, though, right? If it's just a one time thing, he probably got something caught in his throat, like a piece of fur. Especially since it's shedding season in the northern hemisphere. You can give him an egg once a week to help with that. All of it mixed up, or just the yolk (but never just the white).
I agree with Blue. Odds are he had a bit of fur stuck. It can sound really bad.
Ferrets: Contessa Kitties: Watson, Oskar DIP Sinnead, Vincent, Boris, Zeus and Athena, Willow, Mr. Frodo, Indie, Lucrezia, Judge, Odin, Miss Emily, Suki, Cody, Aristotle, Butterscotch, Frankenfurter. RIP Herne, Ligeia, and Mr. Stubbs