I have a fairly new touring bike (bought in May-with barely 100 miles on it.) and it has started making a creaking/rattling (?) noise when I pedal. It's kind of hard to describe.

I can't reproduce it when I'm offthe bike and turn the cranks-yet it doesn't seem to be coming from the seat. Is it possible that the chain needs to be lubed? I'm a beginner with bike repairs/troubleshooting but willing to learn.

The bike was quiet as can be when I first bought it, so this is annoying. I'll take it to the LBS if necessary (they do free adjustments for a year, but are some distance away). I thought I'd get some suggestions from more experienced riders first.