Bicycle Mechanics - Strange noise from rear wheel - any ideas?

Hi all. I'd appreciate any thoughts on what could be causing this noise:

- Fairly loud clicking noise from rear wheel
- Happens both when riding and with wheel lifted and spinning freely
- Irregular, but loosely aligned with the wheel's rotation. Some rotations I'll get one click, around the top of the cycle, sometimes it'll be two close together. Always more or less (but not exactly) at the same point in the rotation

It sounds to me like something small and hard bouncing around inside the rim. The wheel (26" Mavic rims, basic Shimano hub) was handbuilt about 9 months ago at my LBS. I first noticed the noise about 3 months ago and recently it's gotten more noticeable. Performance-wise it's fine, but the noise is getting to be a pain in the ass.

Cheers.

Loose flotsam within rims is common, and it's easy to verify if this is the cause because you won't hear it at higher speeds where it doesn't move. Slowly rotate the wheel and listen for it shifting. If you can hear it, then spin the wheel fast and see if it stops.

If it is within the rim, you can disregard it, try to shake it to the valve hole and out, or if it really bothers you, drill a small hole on the inside of the rim and inject a bit of glue to trap it.

The other place that makes this kind of sound is in the hub, often indicting a broken axle held together by the QR skewer.

If you ride tubulars, sometimes a badly glued zone will make noise on the road but not in a stand, which is very frustrating and makes you look like an idiot when you report the problem and the mechanic can't find it.

Second that broken axle theory. Easy to check: drop the wheel & remove the QR. If the axle is broken, you will be able to pull part of it out of the hub from either side, as they generally break clean through. If it feels OK, then shake the wheel to check for loose bits (spoke nipple, washer, e.g) inside the rim.

Thanks for the great replies. I did try shaking it out of the valve hole - I'll check the axle and if that's OK I'll just give it a little jiggle whenever I have the tire off. Ought to work its way out eventually.