I noticed that it's much easier to put James down for a nap or for bed if there's some white noise or rain noise playing. The noise covers any little creaks or rustles of me leaving the room. For a trip to Marion/Calhoun it would be nice to have rain noise all the time, since it tends to be noisy and busy which gives him trouble sleeping. While we could use a phone or laptop with Spotify, I don't really want to lose access to whatever device we use. Also, rain noise on Spotify is annoyingly always podcasts, which means they end and I don't think they loop. Also, it might auto play something else, it might crash, etc. So a dedicated, stand-alone device would be ideal.
The first iteration used my Teensy 4.0 and Audio board since I've used it for a noise-making project before. I know it has lots of powerful and easy to use software in Arduino IDE, and it can give a headphone output with no soldering/breadboarding/etc.
I started with an old bluetooth speaker with aux in, but it has a physical power switch and the battery only lasts a couple hours. To upgrade I got a power strip with USB charger and a set of USB powered speakers so everything is controlled by the switch on the power strip. Just flip it on and it starts raining.
I made a case to protect it rattling around in my backpack and on random tables and floors, in Enclosure.
I made a loop-able rain noise sample in Audio. It's one minute long and will play on loop forever. The fact that it loops isn't very noticable, since it's just noise anyway.
I made two Arduino sketches in Software. The first one plays a few different kinds of noise. We were only using rain though, which annoyingly wasn't the default. So I made a new sketch that only plays rain noise. I would have edited the original but I didn't have access to it because it was on my desktop at home.
Audio Design Tool contains the documentation for the various audio library objects.
The built-in examples in the Arduino IDE (after installing Teensy extension) are useful. Wav File Player USB was useful for this project, but annoyingly didn't work as-is for the audio board. You need an AudioControlSGTL5000 object and you need to call enable and volume(0.5) on it before you'll get any output. Also, the pin defines for the SD card are for the Teensy 3 version of the audio board, not the Teensy 4.