boys will be boys!!my son is 71/2 still yells and screams and my nephew is the same but he has the sense to go outside and do it.I just camly say(some of the time!!)please take that noise outside as it hurts my ears Or , mummy has a headache take it outside.i think they are just experimenting with the vocal cords and with him not speaking (my son had and still has trouble with speach)it's frustration and he's letting it out don't discourage it as i feel it will hurt the self esteem and self confidence but he needs to know the right places/times to yell.Just consistantancy of letting him know he is too loud and get him to repeat his needs and only answer it when he gets the volume to your liking he will get the gist. consistancy is the only way. boys do take longer to develop and so differently.they are just being themselves the best way they know how .go see your child health nursedoctor and they will refer you to a speach therapist (if you haven't already after the grommets) and they can give you more statigies.