[pulseaudio-discuss] Stream volumes as the universal volume adjustment method

[Jud Craft]

Keep in mind that behind the scenes, when running one program,
Pulseaudio actually treats the device volume as the current
application volume, and scales other applications relative to the
loudest application.

This is because in terms of amplification and quietness, the actual
hardware's dynamic volume range is more important -- ultimate loudness
and quietness will depend on the sound card's capabilities, and not
volume scaling math in the background.

For this reason the predominant application's volume is applied
directly to the hardware, rather than putting it through fancy
mathematics and rescaling.  As far as I understood it, this is what
Pulse actually does by design.  [I could be wrong or misunderstood.]

It just "hides" that fact by using user-visible volume UI that matches
the application volumes relative to the master volume.