it's usually really hard to tell where those sounds are coming from. could be pedals, crank, headset...i had something similar recently, took it to my LBS, and they told me the headset was really dry. they greased it up and the noise went away. now i'm getting creaking in the saddle, and i think it's the seatpost, so i put some carbon paste on and we'll see tomorrow.

bottom line: could be a lot of things. i would either grease everything or take it to your LBS.