Loud free hub suddenly become quiet I have a fulcrum racing 5 evo which has a loud free hub (like other campy) for about 5 years now. I like the loud noise when coasting because I don't need to put a bell on the bike. On my last ride, I just notice that the wheel has become quite (like a shimano).

Can anyone tell me is that something I should be concerned (and get a bell), or is it just need servicing? I also don't know if it's serviceable because it has cartridge bearings. What is happening and how is it affecting the ride?
It's the pawls riding over the catches that make noise. If you hub was previously "loud" and is now quiet, something is likely keeping them from dropping energetically into the catches. I'd disassemble your hub and inspect/clean/relube.

As others (@Daniel R. Hicks) have noted, the issue is that if the pawls aren't catching, the ratcheting systems of the freehub is no longer working properly. As far as bicycle malfunctions go, this isn't the most dangerous thing that can happen as your brakes will still work, steering is unaffected, just a sudden reduction of power to the road.

Whatever is causing this (dirt or rust most likely) is likely to also have secondary effects, chiefly drag, but also the possibility of undue wear on the freehub. Five years is a decent amount of time for water and road grime to make it's way in. You probably don't need to get to your LBS today, but plan on stopping in this week. They should be able to confirm the cause in a few minutes.

Happy Riding.