R A Ellis, any answer might be good enough for you to climb the ratings but it is not specific to the machine model and worse than that is misleading. Generally not helpful.
To Anonymous, your machine does not have the oil holes referred to by RA Ellis: ignore that answer.
What follows is me working on a Bernina 1030 which is very, very similar in this area. An 1130 is slightly fatter at the front to accommodate the electronics on the front panel.
The most likely source of the noise is the idler pulley that links the motor to the rest of the machine. It's perfectly possible to fix this squeak yourself. You will need flat bladed screwdrivers (6mm and 4mm tips are what I used), a thin bladed screwdriver (not a narrow blade but a thin one - see below), a clean rag or tissue, sewing machine oil, and possibly a set of feeler gauges if you want to be really "techy".
Put soft cloth on bench, stand machine on end (don't knock it over). Pull off the two small knobs - don't use a screwdriver to lever them off or you will mark the plastic. Prise out the hand wheel end cover - use your fingernails if possible or possibly the corner of a credit card. Avoid hard edged metal for the same reason as before.
Remove the screw in the centre of the hand wheel (above) and pull out the drive lever: you may need to just prise it up a little at the centre to release it. Pull off the hand wheel. Set the parts aside (below).
Remove the small screw under the hand wheel (above) and the two similar screws underneath (below), all of which retain the end cover. Remove the end cover.
The picture below, from a 1030 shows how the small captive nut is held in the end cover. The 1130 has two. The plastic is not strong so care needed when tightening during reassembly.
Removal of tensioner:
The rather poor picture below shows the 1030 tensioner assembly and tensioning spring. Insert a thin bladed screwdriver between two coils near the bottom and stretch the spring A LITTLE so it can be unhooked. You can remove it from the other end if you wish but don't drop it into the machine.
Using a decent size screwdriver (6mm or a bit bigger), slacken the three big retaining screws that hold the tensioner and remove them all with the washers - don't drop them into the machine. The screws may feel quite tight. Set aside. Disengage the two belts and remove the tensioner assembly (below).
You can see the pulley and you could oil it now. If so, oil BOTH SIDES of the pulley wheel and blot up the excess. One decent drop on each end will suffice. Use sewing machine oil. You will hear Tri-Flow oil recommended by many but this stuff is uncommon in Europe. If in the USA this may be a good choice but I've no personal experience of it. Don't use WD40 or similar - just sewing machine oil.
But if you've come this far:
You can dismantle, clean and make a better job of oiling the assembly. Grab the pulley and try to slide it along the shaft - there's a small amount of end float (I think the Yanks might refer to this as "lash"). You can measure it with a feeler gauge if you have one - I just felt it as the exact amount is not critical - it can't be more than a couple of thou (0.002").
Slacken (half a turn) the grub screw that holds the retaining collar in place and remove it, remove the tufnol washer, the pulley, the tufnol washer and wipe the parts with a clean cloth. Clean the inside of the pulley and notice that the steel plain bearing is in two parts - this is why you need to oil both sides. Replace the washer and the pulley, oil both sides and wipe off excess. Replace the other washer and retaining collar. Tighten the grub screw and make sure that there's a little end float like before. This is important. Check pulley spins freely. The oil will cause some drag.
Hold the tensioner roughly in place and slip the two belts onto the pulley, small belt from the motor first. Put all three fixing screws/washers into place and screw down until very lightly nipped and then back out a quarter to half a turn. Attach the spring to the tensioner and relocate it on it's pin the same way as you took it off.
Retension the drive belts:
Make sure the tensioner fixing screws are not nipping the tensioner. Put the hand wheel onto its shaft but do not fix it. You should be able to move the tensioner around. Rotate the hand wheel a few revolutions and the tensioner will settle into the correct position. Tighten all three screws securely, being mindful that they are going into an alloy casting. That is to say tight but don't strip the alloy thread. Remove the hand wheel.
Refit cover and knobs:
Refit the end cover and again, don't over tighten the screws, particularly this on the bottom. Refit the hand wheel, drive lever and fixing screw. Replace the knobs.
This has taken longer to write than the job takes to do!
Hope this helps. Applies to 10xx series, 11xx and probably the 12xx. Old 9xx similar enough in principle too.