To listen to the sounds from the Bose app library (which are the only sounds you can listen to on these sleeping earbuds) on your Bose Sleepbuds II, you need a bluetooth connection to be active.
The Sleepbuds need to be able to connect to the library on your phone to access the sounds – the sounds can not be stored in the earbuds.
You don’t need an internet connection active when using your Sleepbuds though. Once you’ve got the app on your phone and your chosen sounds in the library ready to go, only bluetooth is needed to make the connection from the app to the Sleepbuds.