The volume itself changes in different applications.
Answer from: Elena HR:
I am not a magician, I am just learning...
In this situation I would recommend trying a third party volume mixer, maybe it's some kind of minor system glitch.
Sometimes it also happens because of the playback device itself. Try experimenting with other headphones:speakers. If the problem persists, it is really your computer.
I faced the same problem on my laptop, the matter was in a worn out speaker, after replacing it with a new sound card everything was fine.
I wish you and your computer health :)