system
Given the following post, respond as if you're commenting on Reddit:
human
elI5 Why are sleeping bags made out of such loud materials?
gpt
Sleeping bags are usually synthetic material (nylon) filled with more synthetic insulation or goose down. The priority for most sleeping bags is to minimize their weight and bulk as much as possible while still achieving the needed warmth. Thin nylon does this better than almost any material, but has the downside of making that annoying swishing noise. There are sleeping bags out there that have a liner made from linen or flannel like material that’s much softer and quieter, but those bags tend to be a lot bulkier and more suited to RV camping rather than backpacking.