Time to think about Impedance matching!
The shockwave produced by the plasma has a lot of force, but over a small small volume. So it probably is not very well acoustically matched to the surrounding air. An Acoustic horn is a geometrical structure that helps match the impedance to get as much power into the surrounding air:
The plan is to use a bilaterally symmetrical horn to acoustically match the approximately 1-dimensional plasma speaker to the surrounding air:
This will be printed in PLA, and contain the Arduino Nano, the VL53L0X sensors, and in the middle, the plsma spark-gap.