Created attachment 178375 [details]
Phone recording of changing volume while playing static noise through speakers.

SUMMARY
When smoothly changing the volume level in plasma, the perceived sound intensity sharply jumps up at certain volume levels. It's most noticeable going from 63% to 64%, but it also happens at other volume levels with a milder effect.
I've attached a video recorded using my phone inside my headphones, since screenrecording isn't affected by the volume level.

STEPS TO REPRODUCE
1. In system settings, set your playback device to "Analog Stereo Output" 
2. Play any sound (preferable static noise for easier comparison)
2. Slowly change volume in plasma between 63% and 64% 

OBSERVED RESULT
Sharp change in perceived sound intensity

EXPECTED RESULT
The same difference in sound intensity between each volume level

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.0
KDE Frameworks Version: 6.10.0
Qt Version: 6.8.2
Kernel Version: 6.13.2-arch1-1 (64-bit)
Graphics Platform: Wayland
Headphones: Logitech G PRO X 2 LIGHTSPEED

ADDITIONAL INFORMATION
I've noticed this ever since i got my current logitech headphones well over a year ago where the built-in volume control actually just sends volume up/down key presses to my PC. The reason i'm using "Analog Stereo Output" is because "Digital Stereo (IEC958) Ouput" is *very* quiet, even at 150% volume, which honestly might be a separate bug i should report.

I set the severity to minor because of how obscure this is, but personally for me i'm constantly distracted and reminded of this bug multiple times every day because 63.5% would be the perfect volume for watching youtube videos for me so i'm constantly going back and forth between 63% and 64% when i can't decide.

The other volume levels this affects but at a lower intensity when going from low to high (subtract 1 if going from high to low):
40%, 45%, 51%, 57%, 59%, 61%, 66%, 69%, 71%, 74%, 77%, 80%, 90%, 97%
(i might have missed some, especially below 40%)