healthy middleage lab respiratory sound laying on side?

recently rescued a 7 year old male lab who was to be put down a his owner died of cancer and the family didn't want to put him in a shelter where he would most likely be put down soon anyway so they were going to expidite the process. he is of healthy weight (88 lbs and dropping with heavy activity daily) when he lays on his side it sounds as though he's breathing through a straw, very audible but seems to have little effect on rate of respiration o effort required to breath. the vet said his heart and lungs sound healthy, Just wanted to know if irs a warning sign of something/ if I should move chest xrays up his vet care priority list or if it's normal for older large dogs to have.audible breathing laying down , seems to not bother him but worries me.