It is the same with my husband - I was accused of whispering, having to repeat stuff, he would get angry, and I would get frustrated. I explained to him that it was his brain's inability to understand what was being said. He does know he has dementia and will even tell people. Now, if I say something, I get him to look at me, and it has improved. I think he's watching my lips and hearing at the same time helps his brain decipher what is being said. If it were essential, I would send him a message to his tablet (he is on it for hours a day), but because he is legally blind, he has trouble reading. His anti-aggression meds have been increased, which has also helped.

Aliwood - You hit the nail on the head there. I speak to him and he doesn't understand, so I either say the same ting louder to be told I am yelling at him, but he still has no clue as to what I am talking about.
The confusing thing is that at other times he has no problem. He does get things confused. The other day he told me that it was on the news that Iran was going to attack Russia. He couldn't get it straight that it was Ukraine and Russia not Iran.
He does that type of thing a lot.

I assume you have checked his ears for earwax. My husband has alot of earwax and when it gets on the eardrums it is like his ability to process info declines tremendously. Ear doctor said it is like he is wearing earplugs. Once earwax is cleared i see an improvement in his processing. He does have cognitive decline and chronic uti's so i have my antenna watching for several issues that may be ocurring. Interesting but ear doctor told me that weekly drops of mineral or olive oil can help prevent earwax buildup.