What are LUFS?
In audio, loudness is measured in LUFS, which stands for Loudness Units Relative to Full Scale. This is a common measurement of loudness introduced by ITU in EBU-R128 - the European standard for audio loudness in broadcasting which was introduced in 2010. The concept of a Loudness Unit (LU) is the same as a Decibel (dB). However, LUs differ to Decibels in that Decibels are a measurement of the level of air pressure generated by sound, whereas LUs are weighted to the real perception of audio by the human ear and allow the measurement of loudness without a reference. In other words, LUFS more closely resemble the way that the human ear perceives loudness. It’s an attempt to correlate our subjective perceptions of loudness with objective physical changes in amplitude.
Introducing LUFS, the measurement, and loudness standards into audio production has helped strengthen and spread the concept of loudness-levelling. The reason for this being introduced was a result of decades of competition to make things louder and louder (known as the ‘Loudness Wars'), which became a source of complaints for listeners. Standards help balance the competition for making things loud, although tools like compressors and limiters can still be used creatively within these standards.
Most delivery platforms, whether in traditional broadcasting or digital streaming, have specific delivery standards for loudness as a quality assurance measure for their audiences. Audio that doesn’t meet these standards is rejected or automatically altered by loudness-leveling normalisation algorithms (which can result in unwanted alterations and artefacts).
Dynamic compression is once again an artistic tool and not a loudness weapon, and it is tools like limiters and loudness meters that aid producers in this respect.