How loud are you?

Seriously, I just completed a voice training class, and it's really astonishing how bad I was at guessing my decibel level (although I was as likely to be too loud as too quiet). Some other people in the class were barely audible even when they claimed it felt like they were shouting.

Get a webcam or smartphone camera, record your normal volume range (from "mouse" to "shout"). If you're hard to hear, get in the habit of taking a breath and using your diaphragm (to me this feels like tensing my stomach to get punched) when speaking. Overdo it for a while.

If you do this and still get ignored, then at least you can cross off the "Too Quiet" hypothesis and keep exploring.