I like this suggestion. It's a perpetual reminder to others that there is a deaf person in their midst.
After the experience of being yelled at by bicyclists riding on sidewalks in Berlin (they use bicycle bells to warn you if they're coming up behind you, of course I don't hear those bells), I wanted to get a tshirt that said "I'm deaf, I can't hear bicycle bells."
One thing I know is that the more people are educated on what it's like to have your hearing loss, the more they would know what to do.
Just saying to someone "I'm deaf, I can't hear you" is not very constructive. It doesn't tell them what they need to do to make sure you can follow. You need to tell them exactly what they should do so you can keep up.
One tip I can suggest is that in situations like sit down dinners, you ask people to look in your direction when they are sharing a story so you can follow more easily and make it clear it's because they matter to you that you want to know what they said.
My best friend always looks at me when talking in social situations and she would explain to others in the group that she was doing that so I could follow. The others in the group started copying her example.
In family situations, they still keep forgetting so I have no problems interrupting and saying "hey, what are you guys talking about?" Other times, if I don't have the energy or patience, I would get up and leave the table. I outright refuse to waste my life putting myself in situations where I'm excluded. I'd far rather read a good book in the livingroom and wait to have one on one chats with family members individually than sit at the table wondering what everyone was laughing about and not being in on the jokes.
I don't get upset or angry because I've learned over the last 40 years that expressing anger or frustration in social situations is not helpful. Anger repels people and they will eventually start avoiding you because you've developed a reputation for being foul-tempered. When you think about it, would you approach anyone at a party who looks pissed off? No, you would be thinking they're ruining the vibe and they should leave if they're so miserable. Would you invite anyone who tends to get pissy at parties and express an inability to socialize well? No.
The other thing that I do is start conversations at parties, not attempt to join them. I may bring up a newsbit or ask people direct questions that is not a yes or no answer, just questions that would get the conversation going and because i was the one asking the questions, they were talking to me and if others joined in, I would hold up a finger and say "hang on, what was that you said?"
When I was in university, I was sad to either not be invited to parties or sad that I couldn't follow others when at parties and realized that this would never change unless I did something to change it then I took charge and was the one who invited others to my parties or invited others to meet for a one on one coffee chats or I was the one who would organize things like going bowling, etc.
When you're in charge, you're the one who sets up the ideal social situations.
It does suck always having to remind people and because this is recent, your hearing loss, it's going to take time for both you and those who know you to adjust to this new reality.