If you hop between two different gyms, there’s a very good chance there will be a perceptible difference in the acoustic qualities between them. One will be better damped than the other, and the better-damped one is normally nicer to use.
Controlling vibration is the key to good damping. When someone drops a heavy-weight, it hits the floor and causes energy transfer. It lands with a fud, and the energy of that sends out vibration. This is why in some gyms you can feel when someone drops a heavy-weight, even when you are at the other side of the room.
Floor vibrations occur when one part of a floor is insufficiently insulated from shock. A dumbbell being dropped is a common cause of floor vibration in gyms. Some vibration, of course, is normal. It is excess vibration we want to control.
The way to control floor vibration in gyms is to design a floor in layers. At the very least, there has to be two insulating layers, so that the top surface (usually rubber tiles or rubber matting) is not in direct contact with the floor.
Some of the rubber flooring systems today contain medium and high-density rubber particles that offer an all-in-one solution, however,rubber underlay is still needed to protect the floor from shock and absorb more energy.
Floor thickness plays an important role in gym acoustic quality because the thicker the floor, the more energy and vibration it can absorb.
For free weight areas and bench areas with weight plates, we recommend 40mm rubber floor tiles with a 10mm underlay / cushioning. You may also need a subfloor or boarding to protect the base floor and spread the evenly.
Powerlifting and deadlift zones will need even thicker floors. We would typically recommend 80mm thick impact protection slabs for these zones. These are installed over the underlay, in place of the normal 40mm tiles.
Walls also play a role in vibration absorption because plates and other things bang into them. You should protect bare walls with acrylic sheet, and you can insulate them with foam to absorb sound and stop vibrations.
Lastly, you should put up signage in your gym, politely reminding people not to drop weights. Signage is the best way to stop dropped weights in the gym, but a well-designed floor will prevent damage if people ignore the rules.