BTW: bc comes with OSX already. To confirm that it's installed open Terminal.app and type
which bc
and hit enter. Should answer:
/usr/bin/bc
So OSX users will just need to install sox.
I just found that there is a sox binary for OSX available too. So - if you don't want to install Xcode and homebrew for just sox, get the sox binaries here:
http://sourceforge.net/projects/sox/