How to deal with a loud fridge when staying in a studio apartment/hotel?

There's no perfect solution, but some ideas:

1. Tweak the fridge thermostat to make it warmer. This will reduce the number of times the noisy fridge motor/compressor needs to run.
2. During the day, place perishable items in the freezer compartment to freeze them solid. At night, when you go to bed, disconnect the fridge power. You'll get a quiet night, and your frozen food should still be cool in the morning. Obvious caveats: not everything freezes well, and defrosted items should never be refrozen. You may also need to deal with condensation/melted water , so a strategically placed towel may help.
3. As a variant of the above, place perishable items in a cooler bag with some ice parks or other frozen items, then turn off power. The fridge will slowly warm up, but the cooler bag contents should stay cool until morning.

Hotels

In a pay/per/night kind of establishment like a hotel, go to the front desk and complain. They should be able to accommodate you (either by moving you to a new room or by swapping the fridge or by reimbursing you some amount).

In the future, be sure to specify that your room be not noisy — away from elevators and the like — when booking it. This will ideally prevent the desk clerk from shrugging and saying, sorry, tough beans.

Apartments

In a landlord kind of establishment like an apartment, inform your landlord. Unless stated otherwise in your contract (US only, IDK about other countries), the landlord is responsible for the general working upkeep of appliances in the apartment.

I've been in apartments where the fridge was crap, and I got a better one off of the local paper / exchange / whatever for cheap. The landlord had always approved the swap for a newer, better model. (But make sure you get permission! Because you can lose your deposit, among other, worse, things if you do it without first getting approval.)

Refrigerators

There are only a very few things that will cause a refrigerator to make loud noises:

• physical damage / bending
• maintenance / de-icing cycle problems
• failing compressor
• something worse that means the fridge is bricked

In the first case, listen to the machine to determine where the noise is coming from. It could simply be that the compressor is causing something to rattle, such as one of the refrigerant lines to knock against the housing. If that is the case, only a very small push or pull to bend the line a little away from the thing it is contacting is all that is needed to quiet it.

(This happens when someone is not careful when transporting the unit. The frame itself can be bent or twisted, or the metal panel around the compressor compartment, or the refrigerant lines themselves — all in ways that are not immediately obvious to the casual observer.)

Fortunately, the lines are very malleable and are designed to bend. Don't be aggressive, though. Just push it only enough to prevent it from striking the frame. If you break it you are liable, and any competent professional who looks at it will know full well that you broke it if you do. And a refrigerant leak is not your friend.

In one case, the compressor was just old and rattling everything. A hard rubber ball from the dollar store jammed between it and the support frame was all that was needed to quiet it down.

De-icing and compressor problems are best fixed by a professional. And a failing refrigerator will be properly diagnosed by one.

In all cases, the owner is responsible for the proper maintenance — he/she just needs to know that maintenance is required.

Some ideas:

1. Move the fridge
2. Move the bed/mattress
3. Wear earplugs (e.g., custom silicon earplugs)
4. Wear earmuffs or noise-cancelling earphones
5. If outside is cold enough, move food to balcony and shut down fridge
6. Add sound barrier screens (but that's hard to carry around unless traveling by car)
7. Add white noise

Check the laws of the country you're staying in. A particularly loud fridge that keeps you from sleeping might be a reason for reimbursement of parts of the payment or the contract in total. With that go to the desk and tell them the fridge is too loud they need to replace it otherwise you refuse payment.
By German law this would enable you to reimburse.

Even if not go to the desk. Getting bad ratings is much worse than a missed payment these days.

3M earplugs in 50/100 boxes for next to nothing and I wear them every day, it's just a habit. go to bed, forgot earplugs? run and get them, sleep perfectly. I wear them all day sometimes, out in the street, in the car, I don't notice I still have them... For sleep they are especially essential. If it's only a noisy fridge, sell it to someone who will put it in a basement and buy another one with a low Db rating, or keep the old one and switch it back when you leave and sell the new one. if the earplugs get tarnished put them in soap water they work many times, you can even find what oil people put on them because they come impregnated with silicon oil or someting.

You can make a heavy box for the fridge if there isn't a cupboard.

I have a very noisy home, a cascade on one side and diesel engines going uphill on the other and resonating in a narrow street.

get a cooler big enough to hold what you need, put ice in it and use it.

Shut off the fridge and turn it back on when you leave.

Very simple and inexpensive.

I do not suggest ear plugs when staying in a rented place(hotel/motel/hostel/B&B) as you do not know the other tenants or employees and their ethics...and I want to be woken up if someone comes in the room or an alarm sounds/gunshots in the hallway, etc...

Look at the fridge yourself. Don't expect the maintenance men to always do their best and their best is usually medicore anyways.

1. Try to level it. If everything else fails, paper inserts under it can help.
2. Look at the compressor and tubing on the rear side. Some noise may be easilly tracked to particular parts bumping each other. These parts can be bent or otherwise neutralized.
3. Try to move the fridge to a place away from bed (if such place exists).
4. Break the fridge and have the landlord replace it with a new one (electrical skills required in order to make it look broken by itself and also has a moral implications).
5. Negotiate with the landlord to replace the fridge yourself (the fridge is probably $50..$150 that may or may not be a big deal for you).
6. The fridge is probably the simplest possible ones with a single volume and single evaporator. You can supplement it's heat capacity by placing cooling packs or some water in a plastic container in the evaporator and/or just dial the setting to the coolest possible. Then simply unplug it for the night.

If you do not have much food, it is often possible to put the food on the window shelf from the outer side for the night. and switch the refrigerator off. For the day, when it may be much warmer and you may not like the food to be visible from outside, you can put it back into the fridge. It works better if you have as single plastic box for all food that stands reliable on the shelf and closes well.