I don't know anyone who likes a squeaky rebounder. Some are really loud and others are whisper quiet. I compare all noise to the Cellerciser that has the quietest noise of all spring rebounders. The Bellicon is the quietest bungee. (The synthetic rubber bungee cords are louder. The natural latex has no off gassing and is super quiet.
I do not recommend using WD-40. This is what most people use. 3n1 oil is my favorite if someone is going to use oil. Graphite is the best but takes so long to apply it as many coats need to be applied. There is a little cheat for those that are too lazy to oil their rebounder.
These can be put on the spring hooks so that there is no noise at all from the springs since the rubber rubs on metal, not metal on metal.
Note: There are videos of the Cellerciser making a really bad noise. When the spring hooks are brand new and not oiled yet, they can be quiet loud. The Cellerciser rebounder does not come oiled and the hooks have not flattened and adapted to the rebounder yet. My Cellerciser is whisper quiet. I bring it in my carrying case into the movies and jump in the corner before you walk in or in some theaters I go to the balcony near the exit and never had anyone complain.
With graphite I only need to do it once every 10 years. It is messy to put on but way worth it if someone doesn't like oiling their rebounder every 2 months. With places that are dusty rebounding can be very loud as the dust soaks up the oil from the rebounder. The Cellerciser is the only rebounder I know of that doesn't have to be oiled that often. When the springs after about 2 to 3 months of jumping on the rebounder, the spring hooks flatten out and become much quieter anyway. Cellerciser springs are very heavy and don't have that high pitch screeching sound that the low carbon springs have.
Also there is one really bad video on the internet showing how springs make really loud noise. If you spray lemon juice on the spring it will make that kind of noise on an un-oiled spring. I know the difference between an un-oiled spring and one that has lemon juice sprayed on it. Not cool.
Note: On some rebounders they are not loud from the springs. Some of the lighter frames are not as grounded and they make noise on certain floors. If the floor is not even they can teeter totter and make a loud noise. this is usually with the screw in legs. The Cellerciser legs have a 360 degree wobble rotation. The ReboundAir is 33 pounds and the 2nd quietest rebounder I tested. At 39 pounds, the Cellerciser is the quietest frame when on floors that are not perfectly even.
If noise is an issue let me know on my rebounder quiz. I will pick out a rebounder based on your answers.
The Lymphaciser and Cellerciser are the 2 quietest rebounders I have tested. The Lymphaciser and Celleciser both have high carbon springs. The Lymphaciser springs have no wiggle room to squeak from side to side. The cellerciser has springs hooks that go into a pin that goes into the frame. The Lymphaciser and the Rebound Air (below) do not have spring hook pins. If you listen to my Rebound Air rebounder review you can hear the noise it makes without the pins that go into the frame. There is no need to put those plastic yellow spring hook covers on these types of rebounders.
The Rebound Air is probably the noisiest rebounder I have ever been on. It is even noisy when doing the Health Bounce. The spring hooks don't have pins that go into the frame and the way it looks I can see that there is way too much wiggle room for the spring hooks to slide back and forth as the rebounder loses its tensile strength over time and the springs stretch out. So, when air born the spring hooks move in the direction of least resistance and when landing the spring hooks can slide to the other end and causing that noise.