Noise from front passenger side found!

After almost a year and several trips to two different dealerships, I found the source of a low metallic noise that seemed to come from the lower part of the front passenger side door. The noise was noticeable during higher speeds on the highway and anytime I encountered rough road conditions. It sounded like a spring vibrating on sheet metal, low but very irritating on long rides.
After tearing down the passenger side door and investigating I found the source of the noise. Underneath the front passenger, between the carpet and bare floor of the cabin is a metal conduit that protects a wiring harness that runs along the floor. This conduit is completely bare metal with no gray foam or coating to insulate it from creating noise. I found that most of the noise is created by the vibration of a single end piece closest to the door opening. It is only held in place by one bolt leaving the opposite end free to bounce around contacting the floor and causing the entire piece to vibrate against the rest of the conduit.
My solution was to use foam tape and felt to insulate the end piece on any contact points between it and the rest of the conduit and to keep it from vibrating on the floor. Sorry the pictures suck but I was in a rush and I had to use my phone. To get to the conduit I ended up removing the passenger seat and lifting the carpet enough to remove the bolt holding the piece in place.