Do You Hear What I Hear?

How do you deal with hearing and noticing in games that don’t have general rules for it?

For instance, D&D and AD&D both have a thief skill called hear (or detect) noise. Obviously this gives them an advantage when listening. But how to other characters hear things? What if a fighter listens at a door. How do you determine if he hears the guards talking on the other side*?

Sure, you could just hand wave it and say, “yeah, that’s loud enough that anyone could hear it.” But where do you draw that line?

Do you have another mechanic that you use? Give non-thieves a 1 in 6 chance to hear? Give them the base, 1st level thief chance? An intelligence check?

I'm curious how other people handle this. 

*It looks like AD&D uses the base thief chance (I never knew this, I just looked it up). I don’t see anything for Basic D&D.