Could be bearings going bad. Could be spokes that weren't stress-relieved pinging. Could be all kinds of things.

Take the wheel off the bike, and spin it. Is there inconsistent resistance? Consistent resistance is drag from the seals (if there are seals). Inconsistent resistance is grit in the bearings.

Check spoke tension again. Check the true again. If all else fails, take it to your LBS and tell them you have noisy wheels. They'll probably know how to fix 'em.