The right answer is, in my experience, something that starts soft and intermittent, and then gradually ramps up in loudness and annoyance. In bed, it's enough to have a harpsichord gently playing, but if I'm watching TV or out at a restaurant I might need it to eventually escalate to a klaxon to get my attention.

My first experience with this was Groovy Blue: https://youtu.be/WCbyp_UuyoM?si=s0ZpfcXZKw7dP17i