Faraday cages and feedback

[WatchCityProfWW]

I plan to mix the MIDI interrupter, a tinyTesla, and Zeppelin Design Labs Altura II MIDI controller for a steampunk exhibition. Since people will be within 3 feet of the finished instrument, I want to use a Faraday cage to prevent damage to cell phones and other devices. My problem is figuring out how close I can bringthe sensing antenna to the coil without degrading response. That will likely set the Faraday cage dimensions.
Any thoughts?

[Moses4525]

I could also use some information on this topic!