Noisy earphones

I use Etymotic Research ER-4S in-the-ear earphones with my iPOD Nano when I walk, but it's annoying that the earphones transmit sound thru the wires/cord. I can hear anything that touches the cord. For example, when I walk, I can hear the cord thru the earphone as it rubs or bounces against my shirt or jacket. It's almost like there's a live feed thru the wire. There is no short that I know of. Could it be that the earphone plug is not grounded with the iPOD and that I need to use an additional jack to properly ground it?