Some sounds play at a very soft volume whereas others play at a normal volume. Examples are, stone and pickup sounds are very, very soft, however, grass and leaf sounds seem fine. Reference here: --> http://www.youtube.com/watch?v=Ohd2jHdqWuY
Steps to Reproduce:
1. Use the OpenAL.dylib file in LWJGL: v2.8.2
2. Place down several different blocks
3. Break them
4. Listen closely for the sounds at a low volume.
Since DB asked in IRC, my 'sound' volume is at 80%, it's not an issue there.