What makes a good alarm clock sound?

The Ringer:

It was inevitable that, in an industry where improving sleep has become its own sub-economy, alarm clock sounds would get disrupted, too. Sure, morning alerts have taken many sonic forms over the course of human civilization, including rooster crows, ringing bells, and Sonny and Cher’s “I Got You, Babe.” But as more Americans become loyal smartphone users — especially the kind that sleep next to their gadget each night — tangible alarm clocks have been replaced with apps that get creative with their morning racket. In this new medium, the strategies for waking up have multiplied, sometimes adopting gimmicky or cruel approaches in the search to answer the same questions: What’s the perfect sound, light, or smell to wake up to?

I use an app called “Rise Alarm Clock“. It has a lovely alarm sound called “Camping Trip” I use to gently wake up to. What alarm clock sounds do you use?