Why are levels so different on popular music tracks I open in my wav editor?

Question

I'm trying to figure out how loud my songs should be. I'm trying to compare my stuff with popular music artists to see how loud their songs are, so I open their songs in my wave editor. When I open Depeche Mode's songs, for example, which I have in FLAC and MP3 format, I see a great discrepancy between average levels on songs of different albums. On some of the albums, the song volumes are clipping like mad!

Why is there this discrepancy between songs-- shouldn't they all be roughly the same?

Why would I see volume clipping in my wave editor for a modern professional song?

When I play those songs back in a media player like iTunes, does it correct the levels or something?

Answer 1

Basically, you're right with all your points.

The level between different albums can indeed be dramatically different, depending on how agressively it was mastered. Records from the early days of CDs are often very quiet (engineers celebrated not having to worry about vinyl's noise floor anymore, and also, early CD players didn't really work reliable with full-scale peaks). Then, until recently, there was a steady trend to master ever louder, with not so good consequences to quality. PCM has a hard restriction on what levels are permissible. If you just increase the volume, you will indeed run into digital clipping which sounds completely horrible, but there are tricks which avoid this; basically all about compression. Brickwall limiters are able to to get virtually all the sound to just-barely-clipping level: enough to make the meters go red, but not really audible as distortion.

Fortunately, the record companies have by now realised that this is not a good idea. Not only is it doubtful whether loud really sells better, also, nowadays a louder recording will in fact not necessarily play back louder – because many audio players do in fact “correct the levels or something”, it's called loudness or RMS normalisation.

Also note that, even without normalisation, different-looking levels may not actually be so different: loudness is a logarithmic scale. 6 dB is not a very dramatic difference in loudness, but correspends to doubling the peak amplitude.

Answer 2

This is kind of difficult to answer, but mainly because you're asking more than one question at a time.

The broad scope that you're referring to is typically known as Dynamic Range. Dynamic range (in laymen terms) is the difference or variation between the minimum & maximum dB levels. In recent years the topic has been the subject of much debate. i.e. Loudness Wars. However, from an engineering perspective the answer is relatively simple; Compression. "Loud" tracks are typically the result of heavy compression in the mixing and/or mastering stages. A compressor is essentially a signal processing device, being used (in this case) to literally squash/compress the audio signal (bringing the peaks and valleys closer together) after which, the supplemental Make-Up Gain is applied, amplifying/increasing the signal, overall.

From various other perspectives, the answer is not quite so straight-forward, however I will say this: The audio used in commercial television & radio advertising is typically heavily compressed in the same manner, so as to stand out above the rest in an effort to capture and/or stimulate the audiences attention. I'll leave you to make of that what you will.

Hope that helps.