I had a similar problem and thought it was the wiper but it was the motor. I am not saying this is your case but you may try opening the wiper arms and have them run to see if they make the noise and also if they seem to slow at some point of the movement. Just remember you have to open the hood for one of them (can't remember if it is the righ or left) be able to be opened.
My car was new and I went nuts cleaning the glass, replacing the rubber wiper part etc and it was that the motor was disaligned.
Good luck and tell me how the test went.