Hi There,
SO here is some fun , Concept to CAD…
Amazing how well it works.
Started out as a question about Sound and ducting and could it apply to Xiao PDM, well IT DOES!,
The code has three Modes, and between Phat fingers and Potato cam you get the drift.. AMA. Round display with a Sound Duct embedded into the base piece. I started with a sweep tube but the channel is way better. 3D printed it and WOWsa it works neat, I had to implement some crude AGC, it lags a little but a WIP… 
Stay tuned, Now it’s going to get fun.
HTH
GL 
PJ