cscommands.comcl_phys_sound_disable_impact_sounds_under_hard_threshold
if true, impact sounds wont play if no soft impact sound is present and the impact is below the hard velocity threshold.
For this command to work you must first run
sv_cheats true in the console. It only works on a local map or a private server — not in matchmaking. sv_cheats is a built-in Valve command and is completely safe from VAC.