Ear problem. Autophony related to PET - Patulous Eustachian tube (http://en.wikipedia.org/wiki/Patulous_Eustachian_tube). Eustachian tube doesn't close leading to loud sounds of breathing in right ear. Usually happens above 1500/2000 meters when exercising strenuously. It's supposedly a rare condition and it can occur from weight loss (I've dropped 10lbs off a fairly lean frame the past 6 months), dehydration (which happens during some runs), and strenuous activity (yep). I'll be tracking it from now on and trying out some treatments (like head between legs and lying down).
stopped running and rested for an hour -- then it went away (just like always) It's usually gone within one hour of stopping. Need to try to shake it on the trail though.