I need help figuring out a noise I have when the brakes are applied. The noise is a very loud whining noise that becomes louder as the car slows down. The brake pads were replaced by an independant mechanic and the noise has been there ever since. I have replaced the rotors and changed the pads to a different brand, but not OEM pads. The noise is still there. Any suggestions? I was advised Mercedes pads would eliminate the problem, is this true? Any help would be appreciated.

It is a late 1994 S320 with about 110K on it.

Thanks