Outside of customers complaining that their rebounder jars and hurts their back, this is another huge complaint about rebounders. No one that I know likes a squeaky rebounder. Some rebounders are very quiet and some are loud no matter how you oil them due to their spring metal composition. As far as bungee rebounders making noise, when the cords get old they make a noise different than a spring but sounds loud. The synthetic bungee cords are much louder but last longer. I prefer the latex bungee cords as they are the quietest as long as their are kept in good condition.
Many people use oil on their springs from the hardware store. This is fine for a high carbon spring but for rebounders that are louder in general, I recommend graphite. It is really messy and takes a long time to apply but it only needs to be done once about every 10 years. This is not needed on single purpose rebounders. The Cellerciser is quiet due to its springs and graphite doesn’t make as much of a difference compared to the the springs that are not digitally tuned. The Health Circulator has super quiet springs and is tuned to Middle C so it doesn’t have that awful noise. The Cellerciser can be very noisy if not oiled. I have brought my Trifold Cellerciser in the movies for years and I do the Health Bounce all the way in the back of the theater. I am always in the back where I am not in front of anyone. Nobody has ever complained or asked me to stop. I am just tired of seeing videos of people comparing noise on rebounders that are fresh out of the box. Of course they will make noise. They are not oiled yet.
Also, if getting a multi purpose rebounder, the rebounder that have pins that hook into the frame are much quieter. Cellerciser spring hooks do not go directly into the frame. They fit into a pin that goes into the frame. This is another reason it is so quiet. It reduces the wiggle room that the spring hooks normally would slide back and forth when one spring engages more when it is at a different tension than the spring next to it.