The spiral falling is the entity trigger_fall which again is set in the map itself. You can change the sounds though :P. I have the lovely Scientist screaming when I fall, funny for 1 minute or so, you get use to it.
<@Miagi> !8 Am I spamming?
<@ChanServ> Miagi: Yes.
<@Miagi> !8 Should I stop?
<@ChanServ> Miagi: Oh, please, PLEASE, make it stop!
<@ChanServ> Miagi: Yes.
<@Miagi> !8 Should I stop?
<@ChanServ> Miagi: Oh, please, PLEASE, make it stop!