Stalin-ohaulic
Banned
I wrote this SPL calculator back in 2005. It will actually get you pretty close. Check it out. I know that it can't be precise due to too many variables not factored in BUT give it a look. Check out the forums. Chat with the Stetsom Rep.
http://ecrack.net/forums/index.php?showtopic=1111
http://ecrack.net/forums/index.php?showtopic=1111