In a lecture last week, I foolishly brought my media player phone (my Galaxy S III) in with its morning alarms activated. So, halfway through the lecture, the phone goes off, complete with the Lady Gaga song I have it set to.
Fortunately for me, my phone was in my bag and that was able to muffle the sound; in addition, my lecturer was talking into the amplifier and I was sat in the back row, as I always am in that particular lecture. My phone's alarm sounded for 30 seconds before switching off automatically and my lecturer did not notice the noise.
It was surprising enough by itself that she didn't hear the commotion but what added to the surprise was that a few minutes later, she politely scolded two people in the front row for talking (she's the type who can tell people off while having a sweet smile on her face and in her tone), as well as scolded two more people for messing around with their phones. In all my lectures so far, this one set the record for the most amount of disruptions and mine wasn't noticed!
In future, I'll be ensuring neither phone goes off in classes, although my Galaxy Note 4 is always set to silent and has only rung in class on silent.