My grandfather in his house has a Cen-Tec CT14DX nozzle made by Panasonic for his VacuMaid central vac, it uses a geared belt. He also has a Panasonic made Kenmore 2621 canister vacuum at his cabin which the nozzle is basically a Cen-Tec CT18DXQD, that one doesn't have a geared belt but rather a Poly-V and it's definitely quieter than the VacuMaid nozzle.
What's the purpose to hear what a split system sounds like? One of the whole ideas of a central vacuum in the first place is to not hear the power unit running while you're vacuuming inside, it reduces the noise. In fact even though the VacuMaid nozzle is technically louder than the Kenmore nozzle, the Kenmore is overall louder to vacuum with because I have the canister running next to the nozzle. That's one of the other reasons why I'd rather not own a split system because I'd want my system to be as quiet as possible. I'd hate to be like the house next door where I'm always hearing the Silent Partner running whenever I go outside, it's pretty loud.