ShutupPortal
Silences portals by default: the sound when one activates and the hum while it's active. Both volumes are settings.ShutupPortal
Portals make a loud sound when they activate and hum while they're active. By default this mod silences both. Only your game changes; other players still hear their portals as usual.
Settings are in com.parallel53.shutupportal.cfg: ActivationVolume (0) and HumVolume (0), each from 0 (silent) to 1 (the game's normal volume). A new HumVolume applies to portals that load after you change it.