The main reasons why a cat's voice becomes hoarse are as follows:
1. If your cat has a cold, fever, or bronchitis, especially during seasonal changes when temperature fluctuations are significant, it's very easy for them to catch a cold and become ill, which can lead to hoarseness. Consult a veterinarian promptly for medication and ensure your cat is kept warm.
2. Cats that meow for too long can also develop hoarseness.
3. The cat's meow is too loud, just like a person's voice will become hoarse if they speak too loudly.
4. If your cat has suffered a trauma or a foreign object is stuck in its throat, you should take it to the vet immediately.
5. Drinking too little water or not drinking water for a long time. 
Symptoms of illness in cats
1. Weight loss: If a cat experiences a rapid loss of weight, it may be related to problems such as parasitic diseases or gastroenteritis.
2. Listlessness: Sick cats are no longer lively; they are lethargic and look sick.
3. Panting: Frequent panting in cats can be related to heartworm, respiratory infections, and cardiopulmonary dysfunction.
4. Loss of appetite: If a cat doesn't like to eat or move around, and also shows signs of illness, it may be related to diseases such as oral diseases, gastroenteritis, or parasites.
5. Diarrhea: If a cat has diarrhea or soft stools several times in a row, it may be suffering from diseases such as dysentery, parvovirus, or canine coronavirus.
6. Persistent vomiting: If a cat suddenly vomits frequently, it may be due to indigestion, intestinal parasites, or gastroenteritis.
7. Excessive tear stains: If a cat has excessive eye discharge and severe tear stains, it is very likely that it has contracted feline panleukopenia, which may be followed by symptoms such as runny nose and fever.
8. Difficulty breathing: Breathing becomes rapid and labored, with open-mouth breathing or abdominal breathing.
