Why are sounds, & my ears, so weird next to a BALLOON?

Question

I work part-time in a party store, and one thing I do is inflate rubber (latex) balloons with a helium tank.

When putting together balloon bouquets, sometimes a balloon gets right near my ear. When this happens, suddenly all sound coming to that ear is muffled and/or distorted in a very weird way! It almost makes my ear feel physically uncomfortable, like something's in my ear that changed the pressure.

I've never noticed this with anything else next to my ear, even big things like pillows or plastic bags. It ONLY happens with latex balloons. I suspect the answer has something to do with physics (a subject never studied by mathematically-challenged me! heh)

Thanks for your help in answering yet another of my eccentric questions! :)

Answer 1

Helium is very light and therefore much less dense than the normal air around you. This means less density for sound to travel across and therefore less noise for your ears.

Answer 2

static electricity!