Default Brightness while talking

Idk why but when i talk my brightness changes to higher value and to automatic when it reaches automatic.
I am using viper 4.1, before was on 1 lower version and same thing. In venom tweaks i am using status bar brightness slider. Alex 2.6 pa3 kernel. Any help ?
Device: HTC One X
Rom: ViperX 4.0.6
Kernel: Alex-V 2.6 pa3


Previous device: HTC Sensation