Although I never had complaints by clients about audio, I always wondered about this...
Volume levels are to easy to determine, since you can see the peak levels. So it's easy to make sure that your whole DVD has a uniformed volume level so the client won't have to keep raising and lowering the audio volume during playback.
But what about all other aspects of audio like bass, treble, high pass, low pass... all these can deceive you if your computer levels are not set right. I have a 3 set speaker system so when not working with headsets, I can raise or lower the bass on the speakers. Now to me, it might sound like I need more bass in my audio and I'll add bass with an EQ, but in reality, it might have just been that my own speakers were set too low on bass and now the client will hear TOO much bass.
See what I'm getting at? Maybe one boosted the bass in the Windows audio settings and now he hears too much bass (even with headsets) and lowers it in his NLE but in reality he didn't have to do this and the client will get bass too low.
We have the same problem with color correction (client TV\Screen shows different colors) and that's why we use a third monitor display, so we can see the actual colors of a TV while editing. But how do we determine a base-line for audio specs? How can we know if we really have audio tweaking to do or our speakers\system is just not set right?