I got the same problem too. Took it to Honda dealer and the mechanic had no idea. I later found out, or at least pretty certain it's the seat belt rubbing against the seats. Just take your seat belt off the holder slot, let it rest it ontop of the slot instead of inside it. The spueaking noise should go away. Hope that helps.

 

Or, as documented in another thread, cut a piece of felt and slip it underneath the seatbelt guide so that the belt rests and rubs on the felt, not the leather seat. This particular problem sounds more like a click than a rattle.

 

I noticed a rattle on my passenger side as well. It was really pissing me off cuz I thought it was the soft top hardware rattling. I realized it was the metal on the seatbelt hitting the plastic. I buckled the seatbelt w/no passenger and the noise was gone.Im gonna get some Brides anyway so hopefully that will take care of that, if not I'll get Takata Harnesses

 

I too, have this annoying sound. On the passager side, behind the seat. i tried cushioning between the seatback, but no luck. its not the seatbelt, either. i tried latching the seatbelt, but to no avail. for me, its not a heavy metallic sound, just a resounding buzz/rattle when i go over bumps in the road (not unlike that heard from license-plate frames from bump'n rides). and no, its NOT from my stereo (i wish!). My car is stock, so its not from any aftermarket upgrades. For those of you who replaced your seats, did that help? hmmm....

 

This is probably caused by a loose spare. Go into your trunk and tighten down the nut that holds the spare in place and that should take care of the rattle. Good luck.

For all those who said they have a seat-belt rattle, it is not in the left shoulder area of the passenger side, but on the right shoulder area. And s/he already said it was not the seat-belt. Here is another thought. Have you looked in the secret compartment? Something could be rattling inside the secret compartment. Take a look in there. But this does not explain the rattle in the left shoulder area of the driver.

 

I've got it too and it's been driving me nuts for over a year now. I originally thought I found it when I discovered a 10mm bolt rolling around in the space between the gas tank and the rear left shock. However, the noise continued and just a month or so ago I literally dismantled just about everything behind the driver's side seat trying to find this rattle. Needless to say, I didn't find a thing. Finally, while driving the car with my wife in the passenger seat, she told me it sounded like it was coming from the back window. So, I reached back and put pressure on the back window while we were driving. The noise seemed to go away. When I took my hand away, it came back. I only hear the noise at about 60-75mph with the top up. When the top is down, no rattle. I believe it to be coming from the top somewhere. It's not the seatbelts as I know what that sounds like and since I wear my seat belt all the time, it'd be impossible since the rattle is coming from behind my head. It is coming from the very back of the top where it meets the car.