Well, as you said, all those different sliders are percentage-based...
...which means it is a relation between the actual sound you hear and the source sound.
- Suppose you play an .mp3 that at most has 60dB with the slider at 50%. Therefore the .mp3 would play at 30dB.
- Suppose you play an .mp3 that at most has 120dB with the slider at 50%. Therefore the .mp3 would play at 60dB.
(note that the math might be a little off, as dB is logarithmic in nature, but then again I don't have a source for this feature. Would make sense that they would alter the dB value rather than calculating the actual intensity, anyways I digress here)
There might be, however, some limits based on hardware that prevent sound higher than a given limit to be reproduced. There exists some hardware that actually amplify the signal the computer is processing, therefore, at 100%, a sound file can give more or less intense sounds in different computers. And there also exists the matter of speaker amplification.
From source to output, one could think of the following diagram:
Source file (.wav, .mp3, etc) > Software volume setting > System volume setting > Audio hardware amplification > Speaker amplification > Sound output
As you can see this gives a lot of turns. Let's make this into an example:
- Assume your file has a maximum intensity of 120dB.
- You hear it in VLC at 50% - So, the sound is now 60dB.
- The system sound (assuming VLC isn't connected to it) is at 50%. So, the sound is now at 30dB.
- The sound board (integrated or otherwise) amplifies the sound by 100% (outputted or inputted sound can be amplified electronically in relative or absolute terms, it depends on the board itself). So now the sound is back at 60dB.
- The speakers amplify the sound 50%. The sound you hear is now at a semi-comfortable 90dB.
(on a personal note, my computer amplifies inputted sound, aka mic sound in absolute terms, at least in Vista. What this does, in comparison to relative amplification, is creating a base signal on which the inputted sound is then added to).
All this is assuming the hardware doesn't cap the signal. If you increase the sound the hardware receives, you can begin to hear a lot more electric noise and the sound will begin to be distorted (akin to successive remastering of records). This is also true for the speakers.
You can see the maximum sound intensity of the audio file using software like Audacity that can edit the audio files.
