As much as typing one sentence and hearing the sounds wasn't bad, and thank god the toggle is actually in the sidebar already. I found it pretty ironic that a distraction free writing interface included obnoxious sound effects.
it's possible to toggle the sound in sidebar (click the button in left top corner)
i actually found the sound effect awkward and unnecessary because the app is called "_Distraction_ Free Writing"
I find that there is something satisfying about the sound of a keyboard. I guess I use to think of it at the sound of progress back in college. :)