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Written from an article by Wallis Hutton, cave research volunteer, Great Basin National Park.
An acoustic monitor in its protective case. NPS/W. Hutton.
What does a cave sound like?
Walk into Lehman Caves and what do you hear? Silence? Your guide and other visitors? Water dripping from stalactites? Footsteps? To find out, the park set out five small, easy-to-place AudioMoth acoustic monitors around the cave. Dr. Steve Taylor came up with the idea and helped place them. The recordings were analyzed with the free, open-source program Audacity.
Why listen to drips
The monitors record .WAV files. They caught the team talking as they set them up, and footsteps of passers-by — but the target was the sound and rate of drips from particular stalactites.
Stalactites grow as calcite, dissolved in water that seeps down from the surface (meteoric water), comes out of solution as the water enters the cave. The drips raise questions:
- How fast do stalactites grow?
- Do they drip all year?
- Do they grow steadily or in spurts — "pun intended," the author notes?
- What controls how fast and how long a stalactite drips?
- What does the drip rate — and so the water flowing through a stalactite — say about its growth?
Five listening posts
The monitors went to five places, near and far from the tour trail, chosen where the drips of one target stalactite might be heard on their own. That didn't always work — especially during the huge snowpack of 2023.
One minute recorded at the Queen's Bathtub on April 10, 2023. Each vertical line is a drip.
What they heard
Spring snowmelt, 2023:
| Site | What the recordings showed |
|---|---|
| Queen's Bathtub | over a month, drips sped up sharply, then slowed back to where they started |
| West Room | a fast drip that stopped abruptly after about a week, leaving only background noise and perhaps faint drips nearby |
| Royal Gorge and Cypress Swamp | too many stalactites dripping into pools or spattering on the floor at once to pick out one |
The spring data also showed how the network could be rearranged, spread out or expanded.
Winter, February–early March 2024: little water was seeping in from above, and the monitors heard very little dripping.
The Queen's Bathtub on March 1, 2024: no drips, and a very quiet cave.
What's next
The early results show that drip rates and amounts differ from site to site. Future work will look at snowmelt, temperature, and each site's depth, as well as how much rock lies above it and how porous and permeable that rock is.
Caves are often thought of as silent places. This study shows that isn't always true — and now there are data to explain why.
Sources
Based on "Sounds in Lehman Caves," by Wallis Hutton, The Midden — Great Basin National Park, Vol. 24, No. 1, Summer 2024, published by the National Park Service and in the public domain; rewritten in hubnx's own words.
I disse publikationerGreat Basin National Park
Licens: CC0 1.0 (offentligt eje) · Bearbejdet efter www.nps.gov
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