Well, that is a bit tough considering that he really can't hear any more, even if he has his hearing aids in... folks in the back seat really can't get his attention at all...
From a few feet away in the front seat, I pretty much have to scream to engage in any sort of conversation...
I always thought voices from the back seat were easier to hear in the front than from the front seat to the back, but maybe that’s just me.
Maybe he’s ignoring them because he only hears voices in certain tonal ranges. Like it’s difficult to hear them if they’re higher or lower in the spectrum. Just a thought, of course, from my own experience.
When I was five, I had an ear infection (?) and it took me quite a few years before I realized that I was partially deaf to low tones. Not noticeably so, but some voices are harder for me to hear than others. I was probably in my late teens when I realized that.
If it’s the case with him, he may not even realize it.