FWIW, there's a connection between hearing and mental sharpness. I found that I couldn't understand the first couple of words someone says, but I could hear the rest once I focused on listening. I read that the ability to quickly change focus could be brain-related so I tried some brain health supplements.
Brain health supplements did not cure the problem, but they helped and I can notice a difference in my mental sharpness within an hour. I take PS™ (phosphatidylserine), huperzine A, vinpocetine, and Quick Brain Nootropic every morning. I'm sure PS work because I have used it in the past to cure "brain fog" in the afternoon after lunch, but you might need to take more than one capsule. I use Life Extension brand. They rate high in independent lab tests.
EDITED TO ADD: I did try three different "hearing aids" off of Amazon. They were worse than nothing. It was like listening to a tinny phone speaker on high volume. I didn't try the $3,000 version because it's easier to just avoid noisy places than to wear a hearing aid.