When Brink starts my sound switches from the headphone jack to the built-in speakers. Brink is the only application I've ever had this issue with. I've seen reports about other audio issues didn't find anything like this. Any ideas?

Processor: Intel Core i7 CPU Q820@1.73GHZ
Memory: 8,00 Gb Ram
Operating system: Windows 7 Enterprise 64 bit
Video Card: NVIDIA Quadro FX 1800M graphics with 1 GB dedicated GDDR5 video memory
Audio: HD audio (HP Previer Sound)

yes , make sure your recording devices are 2 speakers - stereo // right click the white little speaker at task bar then click playback devices then make default the speakers option, confugure it as stereo ,then next , then pick front left and right, then test , then finish. i am not sure if all this might work. check also properties and see what fits best perhaps 16 bit is better.

I had an experience the other day where my squads comms were coming over the speakers (independent of any sfx/music/enemies), whilst everything including comms was coming through my soundcard/headphones and the speakers were disabled through control panel.

EDIT: spelling