Static electricity lowers the volume on iPhone 4S

The situation is the Etymotic hf3 headset used on an iPhone 4S.

As the weather became colder and drier, I noticed that the volume would lower on the iPhone, which was in my pocket as I walked along with my headset on.

Eventually, the volume went to zero.

I could take the iPhone out and increase the volume back up, but it would, over time, go back down.

I also noticed the volume would decrease as I took a sweater (acrylic) off. Again, static electricity.

The problem wouldn't happen if the phone was in my cotton jeans back pocket as that doesn't build up static electricity.

Yesterday, I wrapped the phone in a very slightly damp paper towel and put it in my pocket. The volume didn't decrease.

I've looked all over the Apple support sites, but haven't seen this problem described.

I contacted Etymotic, but they also haven't heard about the problem.

I have no idea what is behind it. The iPhone. My specific iPhone. Having any kind of headset on. Having the hf3 on.

As the winter weather approaches, I would like to have a handle on this.

Right now I'm testing wrapping the phone in a fabric softener dryer sheet.