Facebook is giving my dog anxiety attacks. What can I do to stop it?

[FlyInTheOintment]

I went into my Facebook where the cogwheel thing is in upper right,.I clicked on the notification and unchecked the sound thing...but it is still beeping whenever someone sends me a message on Facebook. I can't stop it, so I have turned off the volume on my computer.

Last night when watching a movie on computer, I had volume up and the noise went off. My dog jumped up from a deep sleep, came running at me ,ears back, jumping on me to pick her up. She was panting and you can see she is scared to death of that one noise. It is so odd since she could hear all sorts of buzz,blips,pings noises etc but the damn Facebook sets her off. It takes a good 15 minutes of holding her to stop her from her anxiety attack.

I really don't want to train her to get used to it as I think that would be too stressful as she is an older dog. Does anyone know how to delete that sound. Like I have said, I've turned it off on Facebook but it is still going off. Is there a sound file that I could change or delete?
This started happening about 2 months ago and it took me a while to figure out what was triggering it. I actually wasted a lot of money at the Vets who told me there was nothing wrong with her.
On the volume mixer i have about 20 internet explorer tabs and they don't say which is Facebook.
just in case you weren't joking, it's just under Account settings notification "How You Get Notifications
On Facebook" and uncheck this: "Play a sound when each new notification is received".


*** I have done that already a few times and it is not stopping it. It sounds odd but I am not kidding...she flips out from that notification sound...no others just that one sound.
It says all notification sounds are off. Yet it is still doing it...very strange?