Sound boo, I think???

Hello all!
I was wondering what do you say when you are not satisfied with something?
I'm making a flash prasentation and when the user enter the right information then it plays an applause sound. I need the opposite sound, but since I don't know how you call it I can't find it :) .
Can someone tell me what to write in google :)
I downloaded the boo.wav in the link below but it isn't what I'm looking for.
http://www.arcanewolf.com/wizard/sounds/

Please help!

a quick google found this

http://www.shoujoai.com/forum/attach...sappointed.wav


wadda ya think ?

:) No, it isn't. You see this is chemistry project and I need something soft to tell: "You are stupid man, don't you get it" But not crying DISSAPOINTED :D
What will you say if you go to the theater and the actors are tirrible? You will not applause them, but hiss them(is it the right word?)
You will do strange noises as you are in the jungle :) Do you get what I mean?