A few years ago I spent three continuous weeks on the Pacific Crest Trail, resupplying through caches so I would never need to go to a town. Afterwards, when people asked me what I liked best about the hike, I told them that it was listening to only natural sounds 24-hours a day for 22 days.

However, on that trip I also experienced several musical brain-worms, songs that acted like a music player stuck on infinite repeat. Each one lasted about 7 days before a new one started up.

To avoid that happening again, I now carry a 1 oz. MP3 player and I listen to a few songs every evening - maybe 15 minutes worth - before I go to sleep. This has stopped the brain-worm problem. YMMV.