Crackling sound heard while no sound playing, with USB audio interface

Ubuntu Studio 24.04
KDE Plasma

I’m using a USB class-compliant audio interface, the Audient iD44 (mk1).
Pipewire settings are: 128 buffer, 48000 Hz sample rate.

While no sound is playing, there is periodically heard a crackling sound, like a frying pan played through reverb fx. It happens for a while and then stops. Then comes back later.

When this happens I usually have Firefox open and some other apps, but no sound playing. Sometimes the DAW is open in the background but with audio device ‘unavailable’, as it’s being used by, I assume, pipewire-pulse.
I am wondering if it has something to do with USB power management after waking from suspend.

Restarting pipewire stops the crackling:
systemctl --user restart wireplumber pipewire pipewire-pulse

But sometimes it comes back later.
I’ve tried changing the pipewire buffer to various sizes. This stops the crackling as I assume it restarts pipewire, but the crackling still seems to come back, but unpredictably.

Not sure how to correctly diagnose the issue?