Highly debatable, depending on how Volume Leveling is achieved, and how and what "normal" is defined. Search the forums here and you'll find lots of deep discussion.
A big debate is about how to define "normal" volume. It is often defined as, loud as possible to overcome circuit noise, without clipping peaks. But details of this get complex fast. Complicating this concept is how the relationship of average and peak volume varies widely among tracks and albums and decades, for many reasons. But what takes it off the rails is how the human ear perceives loudness -- exploited by "loud" TV commercials. So picking a normal music playback volume is based on lots of experience and analysis and conventional practice, but is still arbitrary. MC's default normal volume seems to be an informed, good choice.
MC adjusts volume in 2 steps: one-time track analysis, then real-time track playback.
First MC must analyze every track to determine how far it deviates from MC's notion of "normal" volume: Tools > Advanced Tools > Analyze Audio. MC stores in the database the resulting Replay Gain value of each analyzed track. Nothing permanent happens to the volume of the physical music file.
Then upon playback, if MC's Playback DSP mode Volume Leveling is enabled, MC adjusts the track's volume based on the Replay Gain value, so that every played track is at approximately the normal volume. And since ONLY the playback volume is adjusted, assuming there is no clipping, there is no change in "sound quality".
There are other ways to adjust volume, which some prefer for various reasons:
One method changes the actual music file, permanently resetting its volume similar to how MC does it temporarily during playback. The benefit is that the volume is "normalized" once, therefore plays at the same relative volume on all devices. In contrast, MC's temporary method relies on MC being used for playback (or another player that can also use the Reply Gain value). The criticism of normalizing is that it is a permanent change to the file, which some consider to be a change in audio quality, partly because the file must be rewritten therefore the music portion possibly is changed (or not, depending...) I use this method once in a rare while to "fix" a recording in my library that is way off, because MC's Volume Leveling works best when the total set of tracks varies "some", not "a lot". But I also preserve the original too loud/soft file, just in case.
Another method uses a DSP plug-in to on-the-fly change the music volume upon playback, but using different processing than MC. For instance, I use MC's Volume Leveling as a starting point, but I follow this with another DSP plug-in known as Audio Proc to process music the same way radio stations do, not just at the track level of MC, but at the millisecond level as the song plays, dynamically adjusting both frequencies and volume. I call it "radio station" sound and I like it a lot, but others might not. (I wrote an article about it here:
http://music.advisor.com/story/how-get-radio-station-sound-your-own-music-collection)
You can experiment harmlessly with MC's volume leveling capability. As long as you avoid a normalizing tool that alters the physical files, your music sound quality is not at risk.
Everything I just said is a can of worms, lots of facts and opinions to consider...
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Topic: Does Volume Leveling hurt sound quality? (Read 4613 times)