Just saw your thread pop up at the top of my list and had to comment....
I'm not a medical practitioner and don't have children but I might have been that child that you are describing. I had a lot of ear infections during childhood and at one point was being investigated for hearing issues. I was quite quiet as a child (everyone assumed it was shyness) and my Mum always tells me I was a screamer. I'm not sure if they ever found anything but I had my adenoids removed when I was about five.
My Mum's personality and communication style is the opposite of me. She is an extrovert and will talk constantly, can't stand silence, loves the phone, etc. I am an introvert. I'm happy to be in my own company and entertain myself. I'm very creative and would happily spend hours on my own drawing, painting and making all sorts things (Blue Peter eat your heart out!). This was always a source of extreme concern for my Mum so she was constantly trying to encourage me to put myself forward and be the life and soul of the party. Well, I can tell you I really did try and I probably succeeded as a teen and 20 something. However, I've realised that I like socialising but that it needs to be on my terms or I just get 'peopled out'. I do this by spacing stuff out in my calendar, not seeing people for too long. A hen weekend in Ibiza would probably be my idea of hell!
I've muddled along through life. I was outstanding in Primary, did okay at Secondary although struggled a bit and went onto Uni where I did okay. I've always felt like I am more intelligent than the grades that I achieved or how people perceive me. In terms of work, I've always been in work but I haven't had a great career and have struggled with the environments/people. I've been called "aloof", "misunderstood", "Lady Peekachoochoo" and perceived as a bit stuck up. At times, my communication style is a bit direct but I'm aware of this and try really hard to do the social chit chat because I do really care about people on a personal level Several people have said that they really like me when they get to know me which I can only conclude means that they didn't like me to start with! Several times I've been called a "lovely lady" and a couple of bosses have said I've "got it all".
As you can imagine, this is pretty confusing and I've spent most of my life not knowing who I really am and trying to squeeze my square peg of a body into round holes.
I've suspected for a while that there is something else going on (ASD or ADHD) but I've recently started a new job and it's all come to a bit of a head. I won't go into all the details but I've suddenly realised that many of the things I'm struggling with/have struggled with previously are sensory overload (particularly noise). I find it really hard to filter so open plan offices, MS Teams meetings, interruptions and group stuff where lots of people are talking at once are a bloody nightmare. I really try to keep up but it's like my brain doesn't know what to focus on, can't keep and just ends up shutting down. I then struggle to even think or speak. I sat in some training on Teams the other day and there was so much going on in terms of the pace it was delivered, two presenters, a shared powerpoint (which was too small to see), other attendees, having to type answers in the chat box, having to react, having click boxes on various polls that I mentally shut down about half way through. Conversely, if I know what I'm doing and am left to get on with it I can crash through work at pace. I'm like a bloody robot which I assume is some sort of hyperfocus. I don't think much of this was so much of a problem earlier in my career as the pace of work was slower and information was only really coming in via someone coming up to your desk, letters or phonecalls. Now you have all of that plus emails, MS Teams call, video calls, chats, channels plus all the complicated work systems that you're expected to process and submit work.
I would definitely research ASD for your son. It could be that he hears you but doesn't react (which I do) or it could be that he has retreated inside his head and zones you out (which I do too). I'd test him in different environments. What happens when you are in a room with no distractions and it's been a quiet day? What happens when you've been with lots of people and there's been loads going on? How does he communicate and engage? Does it make any difference?
My ideal world would be to work from home communicating by email with any meetings/calls scheduled in so I can plan for them. If I had my time again I think I would have chosen a career where I could work undisturbed for long periods. Weirdly, I also find physical jobs where I am constantly helps to engage my brain.
No idea if that helps but all the messages I received about being quiet and not speaking up were pretty detrimental for me long term.