Are you on a well? If not a well you can try and replace the fill valve and supply tube. Get a Fluidmaster 400A and a flexable braded stainless steel supply tube. They can be had at any big box store.
Only you will know if you can do it. We can walk you through it if you decide you want to try it, it's not to hard.
My guess is that it only sounds like air as if it was air you would be getting it at other faucets.