Default Hangouts notifications when in app

I don't know if this is the correct forum but I can't think of any other place to put it. Sorry if I'm mistaken.

Thing is, when I'm in the Hangouts app on my phone chatting with someone and that someone replies to me the Hangouts notification comes up. It's weird because I'm on the app, I don't need to be notified for the conversation I'm having on the foreground!

It's so annoying because of the sound and also because of the statusbar constantly switching to show the notification.

Is this normal or is just my phone??

Thanks in advance.
Looking into advanced modding stuff...

Device: GT-i9300 - Dark Blue
ROM: Resurrection Remix 5.1.5 (KK 4.4.2) + Xposed Framework + Gapps Minimal
Kernel: Devil2 2.3.2
Modem: XXUGNA8
Carrier: Movistar (Spain)

Nook Simple Touch: Rooted + Custom Kernel + Gapps