Presumably the pressure wave is maintained by a continuous array of big-ass subwoofers along the whole length of the tube - If this is the case, then keeping the noise pollution down will be a bit of a challenge - unless some sort of active-noise cancellation technology is used for the outside.
Hmmm... This should not be too tricky, since you are generating the original signal yourself, but if one of the exterior noise-cancellation speakers breaks down - it's gonna be LOUD.
Hmmm... This should not be too tricky, since you are generating the original signal yourself, but if one of the exterior noise-cancellation speakers breaks down - it's gonna be LOUD.