Ok, I want to give my players their first dungeon of the campaign. I'd like to have a classic dungeon run with several encounters throughout the dungeon but here's where I'm running into the problem: Once the players engage in the first encounter (read: fight), why wouldn't the rest of the inhabitants of the dungeon run to see what was going on? Perhaps I'm overestimating how far noise travels and how noisy combat is? How do you all deal with this?
Create a natural sound generator, like an underground stream or something, to cancel out the noise.
Generally it's assumed that noise doesn't travel that far, regardless of the real life acoustics of caves.
Although, as someone who has explored caves before, they are nowhere NEAR as echo-y as people normally think. Sound travels, but the twists and turns of a cave reduce its distance somewhat, especially for large caves and caves with lots of rough surface area (like stalactites/mites)
Just because they are neighbors, it doesn't automatically mean everyone gets along.
They could be lazy, they could be busy, etc.
Think about the last time a fire alarm went off in your building. Did everyone immediately run for the exits, or did people make jokes and complain, and see if it was 'for real'?