As someone who’s been hard of hearing since I was about 4, I can say (just for me personally now at 31) that I get a lot of people who feel the need to shout if I happen to forget my hearing aids. Not necessary. Speaking in a lower octave, slower than one would normally but only because it also helps to enunciate each word clearly (for lip reading), to get my attention all my friends have learned to do is raise their hand up like to wave or tap the table (I feel it better than I hear it) or tap my shoulder, and it helps when someone faces me when they are speaking (lip reading and what little sound I can hear isn’t further distorted), and if possible it helps beyond anything else if I can speak with someone without a lot of background noise. That may be unique to me, but I know even if someone is standing right in front of me talking clearly, if there is a ton of background noise? I can’t hear a word. And of course it helps if whoever I have to interact with knows how to sign, but I do still keep a notepad and pen handy for those situations where they are necessary.