That is an incredible demo of how much noise is normally generated by tips travelling at speeds where compressibility becomes an issue. Notice the anhedral tips to shed the vortices further away from the tip for higher efficiency. Without reading up, not sure whether the angled leading and trailing edges benefit vortex shedding (retreating) as well as compressibility (advancing).
Must admit, riff, i'm not sure why use two stroke OPOC when you could use a 4 stroke with very high boost turbocharger. These can be designed to run very quietly indeed. There are various boosted two strokes out there but they never seem to achieve the "theoretical" power/weight benefit claimed for 2-stoke over 4-stroke. Unless this design is already high boosted (maybe with supercharger/decompressor to regulate volume flow rate).