Hunched in a dory dropping into one of the most storied rapids in the world’s grandest canyon, I’m surprised by all that I hear. The crash of water echoes off the granite walls around me, but so do much smaller noises: the creak of the boat’s wood hull, the squeak of the oars, the call of a nearby canyon wren. Maybe the adrenaline crashing through my veins has honed my senses, or maybe it’s sleeping on the banks of the Colorado River under a silent spray of stars. Whatever, everything has become hauntingly loud.