Hi,
In iChat in the iChat menu > Preferences > Alerts the top item is a drop down of Actions
One is "Message Received"
The next line down is Play Sound (A tick box) and another drop down to access sounds.
The list of sound maybe divided into three:-
Those from the App (Named for the actions they go with)
Those from System Alerts (Blow, Frog, Sosumi and the rest)
Those you may have in your Home Folder/Library/Sounds
The default sound is a bit like a "whoop"
The next box/line down in the Alerts pane is the Bounce option
This can be set to bounce the Dock item
That is followed by the AppleScript line.
This can have Auto Accept set so that you don't see the Invite (box floating top right of the Screen for Text Chats).
This may be set against "Text Invitation" which may in turn still have the "Messages Received" sound set to it.

My Messages App may have more app sounds than your version of iChat but other than that the Alert pane has not changed.
The AppleScript item is under the "Play Sound" line I added.
Alternatives
Highlight a Buddy in the Buddy List
Use the CMD and i keys together (Get Info)
In the Info Panel choose Alerts
This method allows you to set Sounds or Actions for Individual Buddies.
Summary.
I am not sure what you mean by "Bubble sound" but you should now be able to find out what it is called (and where it is by where it appears in the List)
It sounds like you might have Applescripts Auto Accept turned On and are not seeing the Invite box
It may also pay to check individual Buddy's settings

9:01 PM Sunday; October 21, 2012
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