You could probably address it in introductions if you want to make your intentions clear (eg. 'Nice to meet you. You may notice I can be a bit boisterous at times, but it's only because I'm passionate. I hope I don't come across as overbearing.') Something like that...
If you're loud and being asked to repeat yourself, as you surmised it's probably not mass hearing-impairment. Personally, I'm prone to talking too softly for some people, but it sounds like you project well.
Is there someone local who'd give you an honest assessment on what the weak points are in your diction?