I always have the same problem with dac output. Game can't initialize it at launch, sometimes, and I have to reboot it.
Try to locate the InstallUtils folder in SteamApps\common\Warhammer 40,000 Inquisitor - Martyr\InstallUtils and install everything there. Hopefully this will fix the problem.
Sound system initialization failed. Please run dxredist from game library. If the problem persists, please try updating the audio driver of your sound car as well.
Would you please share the problem with more details?