How loud is the ABS Self check noise meant to be?

I have a 2005 outlander and after reading the forum I have put the noise down to the ABS self check, however the noise seem to have gotten louder over the past week and a half. Took to Mechanic and they suggested that it was the transmission and that the transmission oil that was in the car was wrong. Have taken to Mitsubishi dealer and they have done a transmission flush and put recommended oil in but still makes noise.

Is this the norm and I shouldn't worry or shall it take the car back?