Loudness war
The loudness war is a trend of increasing audio levels in recorded music, which reduces audio fidelity and—according to many critics—listener enjoyment. Increasing loudness was first reported as early as the 1940s, with respect to mastering practices for 7-inch singles. The maximum peak level of analog recordings such as these is limited by varying specifications of electronic equipment along the chain from source to listener, including vinyl and cassette players. The issue garnered renewed attention starting in the 1990s with the introduction of digital signal processing capable of producing further loudness increases.
With the advent of the compact disc, music is encoded to a digital format with a clearly defined maximum peak amplitude. Once the maximum amplitude of a CD is reached, loudness can be increased still further through signal processing techniques such as dynamic range compression and equalization. Engineers can apply an increasingly high ratio of compression to a recording until it peaks more frequently at the maximum amplitude, a technique colloquially known as brickwalling. In extreme cases, efforts to increase loudness can result in clipping and other audible distortion. Modern recordings that use extreme dynamic range compression and other measures to increase loudness therefore can sacrifice sound quality to loudness. The competitive escalation of loudness has led music fans and members of the musical press to refer to the affected albums as "victims of the loudness war".
History
The practice of focusing on loudness in audio mastering can be traced back to the introduction of the compact disc; however, it also existed to some extent when the vinyl phonograph record was the primary released recording medium and when 7-inch singles were played on jukebox machines in clubs and bars. The so-called wall of sound formula preceded the loudness war, but achieved its goal using a variety of techniques, such as instrument doubling and reverberation, as well as compression.Jukeboxes became popular in the 1940s and were often set to a predetermined level by the owner, so any record that was mastered louder than the others would stand out. Similarly, starting in the 1950s, producers would request louder 7-inch singles so that songs would stand out when auditioned by program directors for radio stations. In particular, many Motown records pushed the limits of how loud records could be made; according to one of their engineers, they were "notorious for cutting some of the hottest 45s in the industry." In the 1960s and 1970s, compilation albums of hits by multiple different artists became popular, and if artists and producers found their song was quieter than others on the compilation, they would insist that their song be remastered to be competitive.
Because of the limitations of the vinyl format, the ability to manipulate loudness was also limited. Attempts to achieve extreme loudness could render the medium unplayable. One example was the hot master of Led Zeppelin II by mastering engineer Bob Ludwig which caused some cartridges to mistrack; the album was recalled and issued with lower compression levels. Digital media such as CDs remove these restrictions and as a result, increasing loudness levels have been a more severe issue in the CD era. Modern computer-based digital audio effects processing allows mastering engineers to have greater direct control over the loudness of a song: for example, a brick-wall limiter can look ahead at an upcoming signal to limit its level.
File:Masvis-zz top-sharp dressed man.gif|thumb|left|Three different releases of ZZ Top's song "Sharp Dressed Man" show increasing loudness over time: 1983–2000–2008.
1980s
Since CDs were not the primary medium for popular music until the late 1980s, there was little motivation for competitive loudness practices then. The common practice of mastering music for CD involved matching the highest peak of a recording at, or close to, digital full scale, and referring to digital levels along the lines of more familiar analog VU meters. When using VU meters, a certain point was used in the same way as the saturation point of analog recording, with several dB of the CD's recording level reserved for amplitude exceeding the saturation point, because digital media cannot exceed 0 decibels relative to full scale. The average RMS level of the average rock song during most of the decade was around −16.8 dBFS.1990s
By the early 1990s, mastering engineers had learned how to optimize for the CD medium and the loudness war had not yet begun in earnest. However, in the early 1990s, CDs with louder music levels began to surface, and CD levels became more and more likely to bump up to the digital limit, resulting in recordings where the peaks on an average rock or beat-heavy pop CD hovered near 0 dBFS, but only occasionally reached it.The concept of making music releases hotter began to appeal to people within the industry, in part because of how noticeably louder some releases had become and also in part because the industry believed that customers preferred louder-sounding CDs, even though that may not have been true. Engineers, musicians, and labels each developed their own ideas of how CDs could be made louder. In 1994, the first digital brick-wall limiter with look-ahead was mass-produced; this feature, since then, has been commonly incorporated in digital mastering limiters and maximizers. While the increase in CD loudness was gradual throughout the 1990s, some opted to push the format to the limit, such as on Oasis's widely popular album Morning Glory?, whose RMS level averaged −8 dBFS on many of its tracks—a rare occurrence, especially in the year it was released. Red Hot Chili Peppers's Californication represented another milestone, with prominent clipping occurring throughout the album.
2000s
By the early 2000s, the loudness war had become fairly widespread, especially with some remastered re-releases and greatest hits collections of older music. In 2008, loud mastering practices received mainstream media attention with the release of Metallica's Death Magnetic album. The CD version of the album has a high average loudness that pushes peaks beyond the point of digital clipping, causing distortion. This was reported by customers and music industry professionals, and covered in multiple international publications, including Rolling Stone, The Wall Street Journal, BBC Radio, Wired, and The Guardian. Ted Jensen, a mastering engineer involved in the Death Magnetic recordings, criticized the approach employed during the production process. When a version of the album without dynamic range compression was included in the downloadable content for the video game Guitar Hero III, copies of this version were actively sought out by those who had already purchased the official CD release. The Guitar Hero version of the album songs exhibit much higher dynamic range and less clipping than those on the CD release, as can be seen from the illustration.In late 2008, mastering engineer Bob Ludwig offered three versions of the Guns N' Roses album Chinese Democracy for approval to co-producers Axl Rose and Caram Costanzo. They selected the one with the least compression. Ludwig wrote, "I was floored when I heard they decided to go with my full dynamics version and the loudness-for-loudness-sake versions be damned." Ludwig said the "fan and press backlash against the recent heavily compressed recordings finally set the context for someone to take a stand and return to putting music and dynamics above sheer level."
2010s
In March 2010, mastering engineer Ian Shepherd organised the first Dynamic Range Day, a day of online activity intended to raise awareness of the issue and promote the idea that "Dynamic music sounds better". The day was a success and its follow-ups in the following years have built on this, gaining industry support from companies like SSL, Bowers & Wilkins, TC Electronic and Shure as well as engineers like Bob Ludwig, Guy Massey and Steve Lillywhite. Shepherd cites research showing there is no connection between sales and loudness, and that people prefer more dynamic music. He also argues that file-based loudness normalization will eventually render the war irrelevant.One of the biggest albums of 2013 was Daft Punk's Random Access Memories, with many reviews commenting on the album's great sound. Mixing engineer Mick Guzauski deliberately chose to use less compression on the project, commenting "We never tried to make it loud and I think it sounds better for it." In January 2014, the album won five Grammy Awards, including Best Engineered Album.
Analysis in the early 2010s suggests that the loudness trend may have peaked around 2005 and subsequently reduced, with a pronounced increase in dynamic range for albums since 2005.
In 2013, mastering engineer Bob Katz predicted that the loudness war would be over by mid-2014, claiming that mandatory use of Sound Check by Apple would lead to producers and mastering engineers to turn down the level of their songs to the standard level, or Apple will do it for them. He believed this would eventually result in producers and engineers making more dynamic masters to take account of this factor.
Earache Records reissued much of its catalog as part of its Full Dynamic Range series, intended to counteract the loudness war and ensure that fans hear the music as it was intended.
2020s
By the late 2010s/early 2020s, most major U.S. streaming services began normalizing audio by default. Target loudness for normalization varies by platform:| Service | Loudness |
| Amazon Music | −13 LUFS |
| Apple Music | −16 LUFS |
| SoundCloud | −14 LUFS |
| Spotify | −14 LUFS, −11 and −19 available in premium |
| Tidal | −14 or −18 LUFS |
| YouTube | −14 LUFS |
| YouTube Music | −7 LUFS |
Measured LUFS may further vary among streaming services due to differing measurement systems and adjustment algorithms. For example, Amazon, Tidal, and YouTube do not increase the volume of tracks.
Some services do not normalize audio; Bandcamp is an example.