Hi, Currently My 6 Year Old Son Has Been Having

hi, currently my 6 year old son has been having trouble hearing at the normal tone I usually speak to him in. i am having to yell at him now, hes usually a really good listener and doesn't select hear. this has been going on about a month, we just went to his doc a couple weeks ago and nothing popped up at the time, I didn't bring up the hearing issue with his doctor.