The click-click-click of a perfectly healthy bicycle hub when slowing down without pedaling.
It's the metaphor sound I use to the feeling of a team working well together: not going to be silent, but you can soundly sleep on it.
The funny grumble my dog makes when he wants me to pet him, and the majestic song of his people my pug can make. Video: https://i.imgur.com/Xh01sK9.mp4
I know it's way too broad and probably very generic of an answer, but music. Cannot live without it since I am pretty much constantly listening to it if I'm not watching a video.
Same. Genre doesn't matter, just match the mood. I've built a library of 250k songs, basically my own Spotify of everything you can think of. I put the Spotify app and plexamp on every device I own, even my work laptop, and have speakers and automation in every room to play Coffee Beats playlists during the day if I don't have anything specific I want to hear at that moment.
The sound of an English country garden on a Sunday in summer.
This is a composite of several sounds all of which must be quiet or distant enough to not be a distraction but which in conjunction are glorious:
childrens’ laughter just far away enough to not be bothersome
bees buzzing from flower to flower
a propeller-driven light aircraft from a nearby aerodrome (ideally this would be a vintage plane with a Merlin engine, gently warbling in the distance)
the sound of leather on willow, and the occasional call and muted cheer, from a cricket match on the village green
the gentle burble of a stream
church bells, far enough away that their individual peels almost blend into each other
the clink of ice as someone pours a perfect gin and tonic.
When I was a kid this was how I knew spring and summer had come. One nested in the trees in our back yard and was very loud. I remember being scared of the sound for a few days before getting used to it.