dB and volume question in iTunes for macOS

[TunesLad]

Is there a brief discussion somewhere of the setting in iTunes: Volume: +/- 0dB? What is accomplished by using iVolume (or other) app to increase or decrease the dB settings of a single music file? Please  don't reference some scientific treatise. There are plenty of those on the web.

[kirkmc]

The only reason I could imagine is if you use Sound Check to normalize volume. Changing the volume on specific files would ensure that they are louder, even after normalization. If you don't use Sound Check, and want volumes to be more consistent in a specific playlist, such as if you are DJing, then it might also be useful. 

[TunesLad]

Being slow to grasp things, I have spent much of the weekend trying to figure out what the db setting on music files is, and how did they get there. Is it volume, is it loudness, can a files dB be manipulated? Maybe I have it, maybe not, anyways, I think an engineer or sound mixer assigns a specific loudness (hopefully amplification without a lot of clipping) to each digital music file when it is created. When I import the music file into iTunes, an Apple algorithm measures its loudness and assigns an average dB value for standard listening on a device. Usually all music files vary in loudness, so rather than constantly forcing me to adjust my device volume as I play my files, I can turn on Sound Check to average all dB settings into one loudness setting, saving me having to adjust the volume for each tune. iVolume allows me to manipulate a single music file, groups of music files, or a total library setting, and even beyond the Apple assigned dB setting. Please correct me if I have misunderstood.

[kirkmc]

It's volume, and, yes, it's easily manipulated. You can do so in an audio editor, or in a playback app or device. 

 

You don't need a third-party app for this; you can access the volume adjustment in iTunes. Select a track, right-click and choose Song Info, click the Options tab and you'll see a slider. 

 

As to why you may want to correct volume, it's because in some cases recordings are released at fairly low (read: normal volumes) and others are quite high (read: compressed), creating a disparity. The lower volume tracks are probably more "correct" than the higher volume tracks. 

[TunesLad]

Volume, loudness, amplified: Aren’t they basically the same?

[kirkmc]

Yes and no. Volume and gain are the same thing; loudness is more relative, and is sometimes used on an amplifier to adjust both low and high frequencies, and not the overall gain. 

[TunesLad]

Appreciate your time and patience, Kirk.