If you want to continue the story; Once you have the pickaxe you have to go to ferreus city, and head west through the mines (you'll be able to get through with the pickaxe.)
The noise and stuff is part of a sidequest. The reward is being able to fight a corrupted Gengar. You'll obtain a gastly once you defeat it.
You exit the cave, and go to the Sage Master's house (it's south-west of pokemart)
talk to her, and you'll trigger the sidequest.
There will be 7 piles of unburied bones through the cave. click on them to bury them.
once you bury all 7, the barrier will go down, and you can battle gengar.