NPC Listening Range

[Rexanilator]

I am curious if there is a way to limit "how far" an NPC can hear commands from players. For example - If I am 6 spaces away and I say HI - then the NPC responds. Would it be possible to limit the NPC to only be able to "hear" if I were just 2 spaces next to the NPC - but on 3 spaces - he cannot "hear" me.

If this is possible...can you say how you do it?

Thanks...and yes, I did search....