seta s_force22kHz "1"
seta s_clipVolumes "1"
Seen these in D3 cfg and the explanation is:
s_force22kHz [0,1] - If set to 1, this forces lower quality (22kHz) audio, which reduces sound quality but improves performance.
s_clipVolumes [0,1] - When set to 1, this removes sounds which cannot be heard which provides optimal performance.