[throwaway4aday]

> it's pretty jarring if anyone can hear it

That's only because you haven't put any effort into sound design. Notification and alert sounds can be horrible like many of the ringtones people choose or they can be pleasant and unobtrusive like certain defaults in various apps. Try browsing some sound effect libraries on various game asset stores, there are many free effects available, and choose something that isn't jarring but is still unique enough to recognize. Avoid sharp beeps and boops or loud melodies, look for ambient sounds like the click of a lock or switch, the swish of paper or fabric, a soft impact sound like dropping a slipper or flip-flop, something you'll notice but won't startle you.