>>> What is your linux DE/ desktop environment (and distro version)?
>
>> I am linux here, and old and good Ubuntu.
>
> I asked what is your distro version and DE, but I didn't get a precise
> answer.
>
> The current Ubuntu is 16.04, which isn't 'old'; and its default DE is
> Unity. In Unity's System Settings is a Sound settings in Hardware and
> there is a 'Sound effects' which has a (separate) volume control for
> Alert sounds which can also be put into the notification area.
>
>
Sorry, I thought it was enough to say that. I use Ubuntu 10.04, with the
DE Gnome 2.?? that comes with it.
The newer Ubuntus (after 11.??) are not good, I do like a bit about
Unity. I would have installed a Linux Mint with MateDesktop, but it did
not work in my computer.
The problem is that: with the system volume controls (all) in 100%, the
sounds Thunderbird makes are not 100% louder. If I set the main volume
to around 30%, Thunderbird sounds are barely hearable. In other words,
Thunderbird sounds are being lower than I expected.
If I play, in Totem (the media player), the same sound file that I
configure Thunderbird to use for one event (message arrived, for
example), it will be played with a lower volume by Thunderbird. I did
this comparison before I started this discussion: open a sounds file
with the media player: its volume at 100%; sound controls all in 100%.
Play it, it is loud. Then I open Thunderbird's
Edit->Preferences->General sound; choose the same file, click to test
it: the volume is lower.
Now I played both sounds (at MP and at TB) at the same time, pausing the
repeating media player a few times to compare more clearly. TB is lower
for some reason.
As the media player has one sound control for itself (for the media it
is playing), separated from the system wide control, Thunderbird should
have one too. I want to set it to 100%, so I do not miss the sound
events for being too relatively low.