Be compassionate
Just as important as where you have the conversation is what emotional state you’re coming from. Telling your loved one that they may have difficulty hearing should not come from a place of frustration. If you’re feeling frustrated, make sure you take time to collect yourself before you have the talk. That way, you’re coming at the issue from a more objective standpoint, which your loved one will be better able to relate to.
It may be beneficial to keep a log of situations and settings you notice your loved one has difficulty hearing in. This can also work as a way to process the frustration and turn it into actionable talking points.