I just upgraded dhewm3 from1.5.0 to 1.5.1_RC2 on my Arch Linux system. While the 1.5.0 was quite quiet already, on 1.5.1_RC2 the sound volume was so low as being nearly inaudible. Because I have a dual-head system, I opened pavucontrol on the secondary screen and started dhewm3. There I noticed that the playback level on dhewm3 audio stream was for some reason set to 60% by default (And I definitely have not set it myself!!!). But, because dhewm3 grabs the mouse, I couldn't re-set the volume normally; I had to SSH in from my laptop and set the volume via a ncurses pulsemixer to 100%.

But still, dhewm3 maximum sound volume is very low, much more silent than on my other games, for example. I had to set the system volume to 120-130% before launching dhewm3 to set the volume about the same level as in other games. I remember the original Doom3 being much louder... (different machine, though). The in-game audio slider is set to max, and there's no difference in volume whether eax is on or not.