Buzzing Guitar

I'm always getting a light buzzing sound from the strings on my guitar, it's only on certain strings, it happens on all open strings and most fretted notes, but i've noticed it's mostly prominent on the wound strings higher up the neck, and on the unwound strings it's on the lower frets so i THINK that the either the truss rod needs to be adjusted or the strings need to be raised. I was just wondering what other people thought about it. I also notice that if I play about 10% of my normal picking using notes that usaully buzz alot, i am able to minimalize the buzzing.