This is a good one! 
My cat snoring when he’s sound asleep.
A well-played bass guitar.
The robins singing early in the morning.
I flew too long in small planes to intrinsically like the sound of sudden silence. :eek:
The sound of skates on ice and baseball cleats (metal ones) on cement. Yep, I’m weird.
The sound of a horse being saddled;
Cards being shuffled;
The thump, thump of the bread machine
A knife chopping up vegetables
Mourning doves. Chickadees. The loons over the lake.
The rhythmic tick tick of my kitchen clock in the complete stillness in the middle of the night.
The Hallelujah Chorus
The low rumbly thunder, as you watch the storms roll in
I miss the morning futzing by my dad at the cabin- kitchen cupboards opening, coffee being made, the clink of his leg brace as he tried to be quiet, his morning ‘talk’ to the various wildlife.
Little kid giggles
My cats chittering at each other
This ones a bit situational.
Hot summer afternoon in Australia, out on a farm: hearing a crow in the middle-distance.
That aaarrrk…aaarrk…maaaaaaaaaaaaarrrrrk brings back a lot of good memories.
The sound of your boots crunching through frosty grass on an early morning walk through the sheep paddocks
Two car related ones - the doppler sound of an old VW Beetle approaching or departing, reminds me of my dad going to and from work.
The sound of a mid-1990’s model diesel Toyota Hi-Lux starting and going into idle.
I’ll take a mellow breeze through pine trees on an otherwise silent day. Brings back memories of hiking/backpacking on family summer vacations to various national parks in the western US.
Thank you for writing “tadak-tadak” because that’s the sound I love and was trying to describe in my post too.
Interesting that you mention humming because, by some miracle, I was the only one getting my haircut at the Great Clips, so it was really quiet other than the radio that was on. My hairdresser started lightly humming along with the music (in tune) and I found it very pleasant and relaxing.
LOVE the sound cleats make when waking on pavement!
Add to my train the sound of planes flying overhead. My work is a stone’s throw from Charlotte International so whenever I am outside walking/eating/whatever I can hear the planes going overhead and it’s such a nice sound to me. If it’s really still I can even hear them idling, which is just as nice to me. Between the trains and the planes I might as well just say “my favorite sounds are commerce”
When racquet meets tennis ball. When wooden bat meets baseball.
And that sudden silence mentioned above–especially when neighbor is done leaf blowing!
Sneakers squeaking on the basketball court. My cats crunching on their dry food.
The intro to Gimme Shelter, or Brown Sugar, knowing that in a matter of seconds, I’ll be rockin ana rollin.
And all the beautiful sounds mentioned above!
I was going to say! Cicadas in the heat of summer at dusk is one of my favorites.
The absolute best is when it’s raining really hard, and I pull into the garage… the sound of the raindrops slowly fades out… great feeling.
One from my childhood, the sound of a rain on the roof of our cabin.
This is really weird. Patricia Neal’s voice. Her voice was similar to my late mothers.
rain on a microphone or a tarp
the crackle of the needle on a record
the crunch and pop of tires on gravel
the chuckle of dove wings
spring peepers
Especially DC-3s, for me. There used to be a cargo company at the airport that had them. I loved the deep, mellow, puttering sound as they rose into the air. It always made me think they were heading off for an Indiana Jones-style adventure. Haven’t heard one in years now. More’s the pity.