This doesn't follow for me. What are you setting the DC at to hear a creature that's invisible or behind a rock that it's less in doubt than if that same creature takes the Hide action, effectively setting the DC 1 above the creature's Stealth check? I mean, the creature could roll a natural 1 on its check. How are you making noticing it less in doubt than that? Are you saying you'd impose disadvantage on a check to notice a hiding creature that's unseen? Because that's, like, the default. You can't even try to hide from a creature that can (clearly) see you.Putting the outcome much more in doubt. Different DCs, advantages and disadvantages exist for a reason. In such a situation hiding roll would represent avoiding to making noise. Now obviously trying to detect someone based on the noise alone is much harder than if you can see them.