I just ended up having permanent hearing loss that I was unaware of until a hearing test. Here is one thing that I learned that surprised me.

I thought that hearing loss was experienced like someone turned down a volume knob. That's not how it works. People experience hearing loss only on certain frequencies. If someone is experiencing hearing loss at high frequencies, they might have trouble hearing only certain sounds like "s" sounds when someone speaks. This leads them to believe that everyone is just mumbling. Because they sound loud, they're just not clear.