Does a tour audio system work underground? Signal, stone and what to carry

"Does it work underground?" is really two questions, and guides who buy the wrong equipment have usually answered only one of them.

The first is connectivity: does the system need the internet? The second is range: how far does its signal reach through rock. A cloud-based audio guide fails the first test at the entrance and never gets to the second. A local system passes the first and then has to earn the second.

Because they stream from a server on the internet. Underground there is no mobile signal, so there is no route to that server, and the audio stops -- usually mid-sentence, at the worst possible moment, with forty people in a corridor.

The distinction that matters when you evaluate a system is where the audio comes from. If the answer is "our servers", coverage is a precondition. If the answer is "the guide's phone", it is not.

Our own system is the third row: the guide's phone runs the server and the audio never leaves the site. That removes the connectivity failure entirely and leaves range as the only thing to manage.

Material and geometry, in that order. Rock and packed earth absorb 2.4 GHz far more aggressively than air, and corners matter more than distance: a signal that reaches thirty metres down a straight corridor may not survive two turns.

This is why the useful mental model underground is not a radius. It is a path. Ask yourself where the group will physically be relative to the network, not how many metres away.

Our field tests at Göbeklitepe and Karahantepe ran with no internet connection at all -- not degraded, absent. That validated the connectivity half: the broadcast does not notice, because the audio path never leaves the site.

The range half is honest work rather than a claim. A local network has limits and rock is unkind to it. The practical answer we arrived at is boring and effective: carry the router with the group, keep it high, and treat corners as the real budget.

If your sites include underground cities, rock-cut churches or long covered passages, the first thing to check is whether your audio depends on the internet. See how the broadcast works -- the guide's phone is the server, and nothing leaves the site.

Connectivity behaviour describes the Your Next Tours system as shipped in 2026: audio is encoded on the guide's phone and served over a local network. Offline operation was verified at Göbeklitepe and Karahantepe with no mobile coverage. Photograph is our own. Range figures are deliberately not published because they depend on site geology and layout.