Playback software like VLC can sometimes process the audio, normalizing the volume levels. Create a DVD export and use that to check.
In PrPro, there are at least 3 ways to adjust the Levels/Volume of the Audio:
- At the Clip-level, one can Rt-click and adjust the Audio Gain. This is often the least desirable method, but can be used.
- At the Clip-level, one can use the fixed Effect>Volume, and easily Keyframe this Effect. This can be done on the Timeline, or via the Effects Control Panel, and this is the most common method. Remember, this is at the Clip-level, so those Keyframes will follow that Clip, should it be moved.
- At the Audio Track-level, one can use the Audio Mixer to automate the Sends, and set Track Keyframes to control the Levels. This will apply Track Keyframes, which will remain on that Track, even if one replaces the Clips on that Track. The frequency of these Track Keyframes can be adjusted in Edit>Preferences. Remember, these are Track Keyframes, unlike the Clip Keyframes above.
The display of either Clip, or Track Volume Keyframes can be toggled in the Track Header.
There are several other Levels/Volume Effects, like Normalize, but they are really something a bit different.
I agree with Jim's suggestion on doing a DVD (I use RW discs to test - no more coasters), and test the Levels on my reference audio system.