Brickwalling

The loudness war (or loudness race) refers to the trend of increasing audio levels in recorded music since the early 1990s, which many critics believe reduces sound quality and listener enjoyment. Increasing loudness was first reported as early as the 1940s, with respect to mastering practices for 7" 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 Compact Cassette players.

With the advent of the Compact Disc (CD), 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 more frequently peaks at the maximum amplitude. 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."

The practice of focusing on loudness in mastering can be traced back to the introduction of the compact disc itself, but also existed to some extent when vinyl was the primary released recording medium and when 7" singles were played on jukebox machines in clubs and bars.

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" singles so that songs would stand out when auditioned by program directors for top 40 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, various artists' hit compilation albums became popular and, when artists and producers found their song was quieter than others on the compilation, they would insist that their song be remastered to be competitive.

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