Habboir posted something using the old way of making ladders..
I know nothing about it my self, I have not looked at the map's VMF..
Have a look your self!
Habboi's map.. No ladder sounds, eh? Use out puts and connect them to an ambient_generic,, I bet there is no sounds that fit your situation,, but,, you could always record your own, and put the whole thing together as a mini-mod!
Happy mapping,