Think its crap blades mostly, i spent about £15-20 on my last set as opposed to £5-10 which you can get, and mine are silent, only time they judder slightly or make a sound is when i accidently wipe a dry screen.

Also last week i used super resin polish on the inside of the windows, and it works fantastic, the glass looks so clean and feels very smooth not tried on the outside though? would it not make the screen go weird when it rains?