If a GPS unit talks in the woods, will anybody hear it?

Not my family, apparently. On a recent hike down to Dark Hollow Falls in Shenandoah National Park, I poked haplessly at the gadget slung around my neck, trying to watch a video on the small screen, while my mom and my boyfriend loped along ahead of my dad and me on the trail. My father, meanwhile, was half-listening to the chipper female voice coming from the machine, but mostly he was checking out the scenery, not the screen.