Mastering is the final stage in the production process. The mastering engineer is charged with several things, including adjusting the overal equalization of the mix, determining fades and spaces between tracks, and adjusting the sound levels of the mixes so that playback over the entire disc is relatively consistent. Since the 1990s, it has become the trend in the music industry to master albums in such a way that they play back as loudly as possible. This is often paired with compression, which is the process of making quiet parts relatively louder, so that there is less of a dynamic range. These are technically separate issues, but both are starting to have a deleterious effect on the quality of recorded popular music (classical and jazz do not yet seeme to have this problem, thankfully). Have you ever turned up a speaker so loud that it starts to crackle from being maxed out? Some rather treacherous mastering engineers have been applying this same principle to a significant number of commercial recordings. The difference is that instead of the playback equipment being maxed out (as in the cranked speaker example), the audio files themselves are maxed out. So no amount of turning the volume down can restore the sound to its proper fidelity.
The poster child for this phenomenom is the Red Hot Chili Peppers album "Californication." The album's high volume no doubt helped it stand out when it was heard over the radio, where sound quality was poor to begin with. Indeed, this is the only reason I can think of to make an album this loud.
Look at the waveform for "Parallel Univserse" from "Californication." It's generally not a good sign when your waveform looks like a solid blue bar. This recording lacks what is called "headroom," which is the space that exists between the top of the waves, and the threshold for maximum loudness.
If you zoom in, you can see that the sound waves are clipped at the top. Important sound information is lost because of this. The waves are not able to form in the natural way, and playback distorted.
Compare that with "Time" from the 30th Anniversary Edition of Pink Floyd's "Dark Side of the Moon" where there is plenty of headroom, and there are no problems with sound waves being cut off at the top.
Clearly Pink Floyd wins the battle for taste (well honestly, what else do you expect?). The Chili Peppers are clearly off the charts, and not in a good way. Ironically enough, I've seem some reviews of the the remastered "Dark Side of the Moon" complain that it is too compressed when compared to the original. I guess back then they actually cared how things sounded. What a novel idea...
There seems to be a perception from many producers and fans that louder recordings are more professional or crisp. Really, the opposite is true. Many recordings sound professional in spite of their excessive loudness, not because of it. Independent musicians may not have access to the same sorts of resources as a band like the Red Hot Chili Peppers, but at least we don't go around saying that our music is awesome because it plays back louder than yours (which, by the way, it usually doesn't).
Maybe this year we can convince Warner Bros. Records to release a new unmastered Thirteenth Anniversary Edition and get the current piece of crap off the market. I was at a party with some of my sister's friends, and one of them talked about how he got "Californication" on vinyl, fulling acknowledging that it was a rather self-defeating exercise. "It's really not a very high-quality recording," is what I remember him saying. I enjoy his sense of humor. Of course, the recording itself is fine as far as I can tell. It's what they did after the fact that's the problem. "Californication" is not the only album that suffers from the Loudness War, but it is one of the earliest and most egregious casualties. Others examples that come to mind include Metallica's "Death Magnetic," Oasis's "What's the Story Morning Glory?," the Mars Volta's "De-Loused in the Comatorium" and pretty much every album by System of a Down. The "Death Magnetic" situation is rather funny, in an unfortunate sort of way. From Wikipedia:
Fans have noted that these sonic problems are not present in the Guitar Hero version of the album, where the tracks are present separately because of the game mechanics and the tracks were sent to the game publishers before the process was made...
...On September 15, 2008, after a reviewer for Swedish daily Sydsvenskan admitted that he preferred the Guitar Hero mixes of Death Magnetic to the official release, a scheduled interview was duly cancelled by Universal Music Sweden. Its president, Per Sundin said:
"The reviewer is referring to a BitTorrent where someone has altered the original songs. The reviewer explains exactly where one should go in order to download the file that totally infringes on a copyright. It's not only an illegal file, but an altered file. The reviewer also writes that this is how the album should have sounded. File-sharing of music is illegal. Period. There's nothing to discuss. That fact – that Sydsvenskan has a writer that has downloaded this music illegally and then makes mention of an illegal site in his review – is totally unacceptable to us."
Given that it is Metallica, after all, this reaction doesn't surprise me. But I would have liked the issue to have been addressed at least on some level. In any case, you know you have a problem when the Wikipedia entry about your album has a separate section for "Sound Quality Issues."
Of course, by singling out the aforementioned albums for their poor mastering jobs, I do not mean to imply in any way that they are musically deficient. Quite the opposite, in fact, and that is the real tragedy.