Earlier quoted context omitted.
How is Soli any different? I know that if I put my hand in this spot and make the motion of turning a dial then it will turn down the volume, and I can hear the volume go down as I do it, whats the difference? Or if I tap the air in a specific way, get an audible tap noise, and know I've completed a preset action (index finger tap = set timer for 5 minutes) its the exact same thing. How is sound feedback not as good?…
Sound is OK for a feedback of success. What we also need is visible affordances -- signals of what can be done, when, where, and how. Also, what I hate the most with these gestures is fearing that I'll get it close but not quite, and something else (or nothing) will happen. With a button, you can feel it and immediately make micro-adjustments while pressing to ensure success. This can possibly be done with sound, but…
I agree with you, sound can be ok as a signal that something has happened. It is fine with some users, but annoys others (beeps when a camera auto focuses, always a split opinion. Some people like it and some don’t).