Both of my children are used to white noise when they sleep. It is part of their bedtime routine and they really like having it. Last night my husband went camping with my daughter for the first time. We do have portable white noise machines, but without electricity, they obviously weren’t of any use. So, hubby devised a white noise stand in. He simply tuned his cell phone radio to a station where there was no signal and thus static. Voila! White noise. Granted, not the best white noise, but my daughter isn’t picky. We’ve successfully used an alarm clock radio in a pinch too. (If it is too “shrill” or “tinny” sounding, then you can throw a shirt over the speaker and it will muffle the sound some.) Again, not a long term solution, but it worked for the night.