Sometimes cats vocalize-make loud noises that at top of their lungs. Sometimes it’s meow, meow, meow meow all coming together. Sometimes it’s just howling.
A cat will vocalize when they are bored or when they are in pain. If you think your cat is just bored, get him or her some new toys. The undercover mouse that is sold on this website is a favorite of my 3 cats. The Panic mouse is another.
On the other hand sometiimes excessive vocalization can be the sign of a medical problem. If your cat vocalizes during or after using the litter box, there may be a problem. If your cat howls incessently, there probably is a medical problem. If you determine your cat is not bored but vocalizes a lot-see your vet.