I have the first edition of "The Master Handbook of Acoustics" dated 1981. I see that the fourth edition is out, dated 2000. Can someone elaborate on what was added/changed in the more recent editions? I am trying to decide if it is worth purchasing the later version. I know that the basics of acoustics have not changed - do the later versions address current topics like HT multichannel, or is most of what was added/changed "fluff?" Thanks.