My cat is losing his voice!

Normally my cat doesn't meow that much except at mealtimes, but for the past two days or so his voice has been sounding hoarse. His meow is barely audible right now. He hasn't been sneezing and doesn't have a runny nose. He is still eating and drinking normally. He is still active and not at all lethargic. The only thing that seems wrong with him is his meow. We recently adopted another kitten in the last month and the two have been play fighting a lot. Both has been hissing/growling at each other in the beginning and I wonder if this might be the reason for his voice loss. We got the new kitten fixed last week and got his shots so the two have been fighting a lot less, but it was a couple days after this that my cat began losing his voice. The kitten is perfectly fine though. Is this something to be concerned about? Will his voice return to normal in a few days?

I am so sorry this happened, maybe your cat's voice is like that cause he meows to loud or your cat has a sour throat?

Please see the vet right now cause this may be serious.