Despite having a 1.1 BigBox which comes with a damper for the Y axis motor, I found I was still getting some vibration from the Y axis which although not massively loud had a particular buzzy quality which was driving me slowly insane. On careful examination, I found that despite being decoupled from the printed mount by the damper the end of the motor was still able to touch the back acrylic panel and hence cause the vibration. The solution was quite simple, I modified the supplied Y axis motor mount by extending the back face that screws to the rear panel by 2mm, and by moving the bottom and front wall out by 2mm each to create a little more space around the motor. This ensures the motor is completely decoupled from the mount and the back wall and has completely eliminated the annoying sounds. I've attached the STL if anyone else should be suffering the same problem.