I like the project, but, I have to say that the budget specified by the author (30$) is unrealistic: only for the electronic board and microphone capsule the expense is 60+E, I just calculate it with a major electronic supplier I'm regular customer. Then you have to spend roughly the same in brass, associated hardware, etc. So we are talking about 120+E ( shipment costs excluded ) and saying that you don't need tools, consumables, etc