Here’s something I hadn’t quite realized while I was at university: iOS alarms and timers will ring out of your loudspeaker, regardless of whether or not earphones are attached (you’ll just hear a sound in your ears, too). It’s becoming more well known that iOS alarms will ring right through silent mode (NYC’s Philharmonic Orchestra found this out earlier this year), but I had assumed that all sounds were re-routed to the headphone jack whenever earphones were plugged in. That’s not the case. Alarms and timers will always ring from the device speakers, regardless of the status of the silent switch or the presence of something in your headphone jack
There are two takeaways from this lesson: the first is that you shouldn’t set up alarms or timers to ring at the library like I did in university (apologies to everyone around me, ever) and the second is that you can safely fall asleep with headphones on, if your want to – after all, if they should fall off during the night, your alarm will still be blaring through your phone in the morning.