Could it be allergies? A new enviroment could have something that he is allergic to or if it is in a new area. That could also explaine the change in his voice and coughing. Ask you vet about giving him some Benydril (? spelling), 1/2 a teaspoon for a cat I think (maybe one of the kitty experts can verify that amount)

That picture is just to cute! Looks like he just fits in that basket and that look on his face is priceless!!