How to communicate PTSD triggers to someone?

My patner helps a lot with my ptsd symptoms. The first time it came up was a week in and i freaked out bc they raised their voice. I explained to them, and since then its never been an issue. Sensitivities/triggers of mine just kinda came up as our relationship went along, and theyve always been respected. They have def triggered me, even 2 years later, but never on purpose, just bc i have a lotta stuff. Anyways, obv not every person will be kind, but its def worth a shot communicating. And try to be clear about at least the general reason why, so they see where its coming from. Thats been important in my experience. You dont owe ANYONE ur story, but a brief explanation can help a lot especially at first