Cocoa Touch: How can I access resource sub-directory?

Question

Currently I am working on iPad. In the Resources folder of project, I have a sub-directory "sounds". How can I access it to get the contents of this sub-directory?

I have tried:

NSArray *array = [fileManager directoryContentsAtPath:
                  [[[NSBundle mainBundle] bundlePath]
                    stringByAppendingString:@"sounds"]];

But the array I got is empty. Anyone know a solution?

Thank for your help.

Thank you.