In your "
Amnesia the Dark Descent" 
directory root, open up the 
ModelEditor. (
If you haven't already downloaded it from the wiki .)
Do "
File>
Open" and find the "
batteries" (
Extension = 
.ent) in the folder it is located in.
At the top menu, click "
Settings>
User Defined Variables".
You should see in the top left "
Type" and the word "
Item" displayed to it's right. To the right of that is "
SubType" and 
possibly "
HandObject to it's right.
Below, scroll down and find the "
PickSound", you can change the sound pickup their.