by NZcaver » Jan 30, 2022 4:03 pm
Hi Peter,
Interesting concept, thanks for sharing. I don't know if this has been tried before. Give it a shot!
This is not my area of expertise at all, so take my thoughts with a grain of salt. I think you'll run into some issues not all that dissimilar to traditional cave radio. Vibration conduction will surely be affected by geology, and particularly by changes in geology between the transmitter and receiver. Variations in rock, soil, voids, etc. Also I assume acoustic vibrations will propagate quite differently in limestone vs marble vs granite vs lava etc. Like radio waves do (or don't).
The other challenge you'll likely have to overcome is interference, both man-made and natural (seismic). We can't call this RFI, so maybe AVI (Acoustic Vibration Interference)? I can only imagine what other sources of noise/vibration will be picked up by a very sensitive acoustic receiver, and then the processor will need to do its magic separating the signal from the noise. Like we found with VLF, this may affect the surface station (receiving) a lot more than the underground station.
Really to be sure any system like this will work in the event of a cave rescue, it will need to be pre-tested in specific locations in that cave. Otherwise, as with traditional cave radio, you'll be taking a chance on whether or not comms will work when you most need them. Good luck!