How could speed up and slow down a timer by distance to actor.

good advice.
I already have a system where the player will be detected by distance, But I want something more organic and less robotic.
My idea is to have a icon above the AI head that once filled up is an instant detection.
My goal would be to scale my distance from between 1 meter and 30 and map range clamp to the value my eye meter fills up.
I have already tried this approach but it didnt work yet.
I have seen a system like this In metal gear solid 5 and the last of us.