Pulse Audio is another layer on top of Alsa, and the user can control the sound system through Pulse Audio's GUI.
The options are exposed to the user through PulseAudio Volume Control and a couple of other utilities such as PAPrefs, PulseAudio Manager & PulseAudio Equaliser.
You need to install PA Vol Ctrl and get to know its functions in order to appreciate what it allows the user to manage ..... not only volume .... but also how the sound stream is managed from any source and to any sound device attached to the system.
It is particularly useful for managing sound to and from USB attached devices such as speakers and wireless headphones as well as Bluetooth connected devices.
So my advice is to install the pavucontrol package from Synaptic and get to know it.
You might find it makes things much easier to manage.