Thumping noise in system sound notifications - Sound / audio issues

Operating System: Kubuntu 24.04
KDE Plasma Version: 5.27.12
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Kernel Version: 6.8.0-94-generic (64-bit)
New installation

Onboard Audio (Realtek ALC221 codec)

Generally audio works - e.g. I can listen to a video with good sound

The problem is at beginning of every audio and the system sounds

  • System notification sounds give a thumping noise.
  • examples:
    • the sound after boot or the sound on receiving an email is a thumping noise. This noise is not then followed with a default notification sound.
    • Starting a video with sound such a youtube in Firefox, first has a thumping noise, then the audio starts (without noise)
    • in Audio - system settings, trying a sound test, the first test starts with a thumping noise and continues with the test sound; as long as the window has not been closed on subsequent tests there is no thumping noise, just the test sound. If the window is closed and reopened, the same pattern is repeated.

The thumping noise is just annoying, the applications work.

On a previous Kubuntu 24.04 upgraded from 22.04 on a different machine, there was no problem.

Tests:

I reinstalled: :~$ sudo apt install --reinstall sound-theme-freedesktop

Also pipewire is running

but I have adjusted the configuration to increase audio buffer size, as a test:

default.clock.rate = 48000

default.clock.quantum = 1024

default.clock.min-quantum = 32

default.clock.max-quantum = 2048

This has not made a difference.

Has anyone come across this issue, is there a solution?