I voted for the RF one - although I'm not that into RF, but it's the only one with robots mentioned. Not sure how RF and robots go together so some mind boggling might be needed if this is selected.
Having an experimenting with sound competition could include anything with sound. Like you mentioned, acoustics would be part of it. Sound vibrations has so many different project possibilities. A few years back I integrated sound waves into a water tap to watch the different results.
Anything having to do with sound sounds very interesting! Something similar to the Acoustics competition we had this time last year I imagine? Or, did you have something different in mind?
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