cat noise

Question
We have a 13 year old cat, who was fine before we moved. Since moving he has made this loud bellowing noise. Like when 2 cats are mating!
He has been nuted and is very good health
What or why in your opinion is the reason for this horrible shril. He does it mostly at night or sometimes after eating

Answer
My sisters cat is just like that and my only conclusion is your cat doesn't like your new home he may have left something that he really likes at his old home and feels lonely, but in reality i could be wrong but thats the only reason I can think of, just try giving him more attention then usually or get something that was associated with your last house.