The only real way ive found to make 99% sure something isnt taken the wrong way is to turn the potential insult around on yourself. I have also found that statements proposed as questions work better than outright asking something, as it sounds less accusatory for whatever reason, less direct I suppose.

So both rules together is something like "I'm so sorry, I feel like I sometimes talk too quietly, hopefully eveything made sense?"

For sure it's not perfect, just like other phrasings the person could take you up on your deflective answer and have you repeat it (good ending) or pretend that they in fact were listening and lie out of pride (bad ending)

But you're almost guaranteed to not insult them!