If you spend much time in a woods, you start to realize that the sounds that travel the furthest are ones that sound like drums. Is it a coincidence that Native Americans frequently used drums? No — they were definitely used for long-distance communication.
Elephants, whales, and other animals use infrasound to communicate over very long distances. Low-frequency sounds travel further than high-frequency ones.
emergency backpacking drum
So the question arises — is it possible to create a collapsible drum that can be used by a backpacker for emergency communication? The typical emergency signalling devices are whistles (high frequency, so it won't travel as far) and mirrors, but a drum could be a useful addition.
I'm stopping work on this, and I haven't implemented or even refined the idea much. But the current design is:
- drum body — Carry a Fiskars saw in your pack. In an emergency, look for a tree or log that has a hollow center (due to fungus or several other reasons), that still has sturdy outsides (ie. hasn't been rotting for too long), and is the right diameter. Cut a ~8" tall section out of this log. (note: I carry a Fiskars with me normally, since I believe it's important to be able to build pioneering-style objects, if some sort of emergency requires it. So I don't count the Fiskars as part of the weight of a packed drum)
- drum head — This will have to be packed, since the drum's performance depends a lot on the drum head material, and it's hard to create this in the field. THESE INSTRUCTIONS seem really good. Fiber reinforced silicone is a material that's definitely used by professionals. That instructable provides a pretty cheap way to get exactly what you want.
- A silicone sheet is going to have some noticeable weight to it. So use the thinest sheet you can, but be aware that packing a drum is going to have an unavoidable cost.
- Tensioning mechanism — Ropes, strung around the base of the drum, would be used to tension the drum head. To make this work well, small grommet-style features would be attached around the outside of the drumhead. These could be normal metal grommets, but they could also be heavy canvas that's sewn onto the base material BEFORE coating it with silicone.