Earlier quoted context omitted.
It would be nice if there was a way to check the system audio volume via the web audio API. Then you could display a notice only if the volume is too low or too high. Alas, no such functionality currently exists without browser plugins.
I would agree that it would be nice to have an option to check if sound is not muted, but not to actually check the volume. One of the worst user experiences I have experienced in the recent years is those notifications telling me that my volume is too loud. But such assumption most of the time is totally wrong as it is hardware dependent. Especially when you use additional speakers or headphones with their own volum…
I wonder what the potential output volume range for unpowered headphones is for the volume set at, say, 40% in windows.