As much as I support flexibility and making difficulty a user choice, I believe this is something that could greatly ruin the experience. The best thing about TDM and its stealth methanics is realism and attention to detail... which strongly includes relying on sounds made by enemies, and enemies being able to hear noises you make. It has to require audio not just for eye candy, but for the game's mechanics and gameplay to function well.
There could however be a solution, which as long as it's optional I would not oppose: HUD waypoints that flash to indicate the intensity and location of sounds made by NPC's. Off by default of course, but it could be part of an "easy mode" especially for people with no audio. With TDM it's usually harder to find developers willing to implement other people's suggestions however, so finding someone to do this might also take time.
Edited by MirceaKitsune, 26 September 2015 - 12:48 PM.