Consider following case
I am listening to music on
xfce 4.12. The sound level is on 25% of the maximum in
ALSA Mixer. Suddenly, an application [I reproduced it using two different applications] gives a loud warning sound. I open
ALSA Mixer, and it seems that the sound level has automatically been set to 100%.
After this incident, I manually put the sound level on 25%, but cannot hear the music anymore. If I set it to 100%, I hear a sound level that corresponds to what used to be 25% before the incident.
What did happen? Is it possible to prevent this from happening again (in order to save your ears)?
The installed ALSA version is
k4.9.0-5-amd64(see this question).
This happened for instance while listening to music on 25%. I downloaded a file and opened it in Okular. The sound level was set to 100% and a warning (with sound) told me that Okular could not open the file.
It happened again in Konqueror when it opened an error
Security Information - Konqueror
You are about to leave secure mode. Transmissions will no longer be encrypted.
This means that a third party could observe your data in transit."