humming

I have a 1996 2 door cavalier andit is making a humming noise when im going between 35 and 50. The humming like gets high and low and switches about every second. It gets faster when im nearing 50. Does anyone know what this could be from? I cant really tell where its coming from. thanks

It sounds like alternator noise.

have you changed your tires when you get a set of new tires they will make that noise

well they are pretty new...and i forgot air was just added...that must be it... i just didnt think they would because it was changing high to low like to slow to be tire noise...but that might be it