I have several USB headsets, which are supported by the snd_usb_audio driver in
the kernel and do work under Linux.

They also work on my system if it is freshly booted and has not been running
for a long time. After this, plugging in the headset causes this error in
PulseAudio:

> E: [pulseaudio] module.c: Failed to load module "module-alsa-card" (argument: "device_id="2" name="usb-C-Media_Electronics_Inc._USB_Audio_Device-00" card_name="alsa_card.usb-C-Media_Electronics_Inc._USB_Audio_Device-00" namereg_fail=false tsched=yes fixed_latency_range=no ignore_dB=no deferred_volume=yes use_ucm=yes avoid_resampling=no card_properties="module-udev-detect.discovered=1""): initialization failed.
> I: [pulseaudio] module-udev-detect.c: Card /devices/pci0000:00/0000:00:08.1/0000:05:00.3/usb1/1-1/1-1.3/1-1.3:1.0/sound/card2 (alsa_card.usb-C-Media_Electronics_Inc._USB_Audio_Device-00) failed to load module.

Trying to load module-alsa-card manually also results in an initialization
error.

But the headset can be put to work by loading module-alsa-source and
module-alsa-sink manually:

> pactl load-module module-alsa-source device=front:CARD=Device,DEV=0 namereg_fail=false tsched=yes fixed_latency_range=no ignore_dB=no deferred_volume=yes
> pactl load-module module-alsa-sink device=front:CARD=Device,DEV=0 namereg_fail=false tsched=yes fixed_latency_range=no ignore_dB=no deferred_volume=yes

The device name has been determined using `aplay -L` and `arecord -L`.

But if the headset is initialized manually, the volume is reduced, which is
somewhat OK for the speakers but makes the microphone more or less unusable.

I'm running a fully updated openSUSE Leap 15.2, PulseAudio version is
pulseaudio 13.0-rebootstrapped.