Suggestion: Sound Notifications Timer

Hey, as it is now, if a friends sends 5 message in 5 sec, you get 5 x Sound notifications, not every one seems to know the SHIFT + Enter options, or does not care, this is annoying if you have friends that types all the times...

If you look at the Options > Appearance > Change Font Scaling, there is this nice slider.

I would like to see a slider like that under Notifications, where instead of font size, you set number of seconds between the sound notifications, like if a friends want to type 5 message in 10 sec, and you have set the slider to 20 sec, it will NOT make a sound for every 5 message, but only the first one, since the settings is set to 20 sec between every new notification from that friend.

I know you can mute the friend for x min or x hours, but this does not help much, i do like to know a friend have send me a message, after all they are friends right?
Muting them totally, yeah well seems a bit hard, all i need is not to know about every message they may send if they decide to type like

Hey
You there
I send you 2 message 0.002 sec ago
Still not answering me
its been a whole sec now, since i wrote the first message...

Well you know, people :D

So please a sound notification slider, 5, 10, 15,20, 30, 1 min, 5 min... or some like that, between the notification sound