customizing iCal alert sound

[R.Welz]

Hello all.

Unfortunately it seems that iCal alert doesn't recognize my own sounds. I
have some in Library/Sounds.
Since iCal.app is a package, it should be possible to insert my own sounds
into some resource? But I don't know where. Or is there a better place for
my own alert sound?

Thanks for help.
Robert Welz