Turn off radio and AC then record us a video so we can hear the sound you have.
I hope its something as simple as DMF or so, but because you say you only hear it in 2,3 and 4 it could be something inside the gearbox. Certain gears inside the box will box will be shared by the eventual 2,3 and 4 gears, depending on the gearbox. I am no expert on the 325 5speed but I assume it is a similar concept. Like 1st and reverse should share some gears, with reverse having 1 extra to change the direction on the output side.
Best to get it checked asap before you cause more damage.