I am trying to build microphone capsules in my garage. Trying to go below 14dB (Primo EM272 level), under 1". It is difficult but rewarding. I do not expect any financial benefits from it, even if I make it under 10mm, because it is very time-consuming. Big players already have massive factories doing 10,000x of what I am doing.

This is the most niche tech-related hobby I have currently.