While it would be nice to have a No SFX or even an alternate SFX option in the CC, you can get around it my changing it yourself in your game folder. Just need a 1 sec silence.ogg to then rename to the appropriate SFX file name and drop it in the correct sub-folder in your data\sounds\ogg\ location. Example, the fly SFX listed below would go into data\sounds\ogg\powers sub-folder.
If you've added mods, then you should already have a data folder, if you have not modified any sounds, then you'd have to create the rest of those sub-folders.
Folder name: powers
File names: air_loop.ogg, Flight1.ogg, Flight_loop.ogg, Flight1_loop.ogg, Flight2_loop.ogg, Flight3_loop.ogg, Groupfly_loop.ogg, Hover_loop.ogg