Made me smile Jonathan thank you.

With regards to extrusion, if your going to do it, use shielded cables to do it. Im thinking that any noise that dose get in, may echo like sound in a tunnel, then you may get an echo of an echo and so on and so on, leading to an amplification? If the end of the tunnel is of a blind type, the noise cant escape ?

There maybe other complications to, access being the first to come to mind.

Lee