Sorry, but it isn't THEIR hearing that is the problem!

Think about it for a minute... Most of us sing pretty strong. The mike and the monitoring is set up to be optimized for this. Then you use the SAME settings to talk into. And few of us talk as loudly as when we sing. Here's the problem.

TBH, the only way you can effectively overcome this is to talk a LOT louder and clearer than you normally do. It's called 'projecting' and is a standard technique for theater performers who aren't miked. A good actor will fill a theater with just his spoken voice, and not sound like he is shouting. But converse in their normal voice, only the first few rows will hear a thing.

Go and see most bands, solo performers, anyone with no soundman to ride the levels, and you will see that not being heard well while talking is a usual occurrence! The way to fix it is not with technology (all a compressor will do is boost gain when you talk quietly, which will usually mean a ton of feedback), but by working on learning to talk clearer and LOUDER! Understand that, when on stage, between numbers, you aren't having a conversation in your living room... You are in a theater, trying to project to the back seats!