By default, pulseaudio will shift to alternate-sample-rate if the first audio playback stream does not match default-sample-rate.
With the "show volume meters" option enabled in pavucontrol, it will lock the rate to default-sample-rate, other streams are resampled to that default rate.
Code:
I: [pulseaudio] sink-input.c: Trying to change sample spec
I: [pulseaudio] sink.c: Cannot update sample spec, monitor source is RUNNING
I: [pulseaudio] speex.c: Choosing speex quality setting 1.
If run pavucontrol after audio playback stream which at alternate sample rate, resampling will be at that rate too.
Code:
I: [pulseaudio] source-output.c: Trying to change sample spec
I: [pulseaudio] source.c: Cannot update sample spec, SOURCE_IS_RUNNING, will keep using s16le and 48000 Hz
I: [pulseaudio] speex.c: Choosing speex quality setting 1.
So, disable "show volume meters" option.
I also found some plugins will lock sample rate:
cava, compressor from calf-ladspa.
