Really hard to say what is actually making the sound (belt, guide, internal part?). If you bought from Home Depot, they will just exchange. Take it to a Honda Dealer for possible warranty repairs. If nothing else, a trained tech at the dealer would be able to tell you if the sound is "normal' or not.
I bought it at Home Depot so I'll more than likely just exchange it. I did make a short video of the noise. This is with out the blades on. The noise sounds way louder in person than on video. I did notice if you lift the mower up it doesn't make the noise but once it touches the ground and has some resistance it makes the noise. It's worse at low speeds. Here is the video.
http://m.youtube.com/watch?v=FwWSJwzfmaM&feature=youtu.be