Ending the ‘Loudness Wars’
For years, audio for broadcast and music was governed by a simple principle: louder is better. Mixers would use heavy compression and limiting to maximize the signal’s level, pushing it as close as possible to the digital maximum of 0 dBFS (Decibels Full Scale). This led to the infamous ‘Loudness Wars,’ where commercials would sound drastically louder than the TV show they interrupted, and music became dynamically flat and fatiguing to listen to. The problem was that measuring by peak levels doesn’t reflect how humans actually perceive sound; we perceive loudness based on the average energy over time, not just the loudest instantaneous peak.
To solve this, international broadcast unions developed a new measurement standard (codified in standards like EBU R 128 and ITU-R BS.1770) based on perceived loudness. This new system uses a sophisticated algorithm that models human hearing, paying more attention to the midrange frequencies we are most sensitive to. The units used in this system are Loudness Units.
LUFS, LU, and True Peak: The Modern Metering Trinity
When working with loudness, there are a few key terms that a modern sound mixer lives by:
- LUFS (Loudness Units Full Scale): This is an absolute measurement that sets the target for a program. Every major streaming and broadcast network has a specific LUFS target for all content delivered to them. For example, Netflix specifies an integrated loudness of -27 LUFS, while Spotify aims for -14 LUFS. The goal of the mixer is to have the average loudness of their entire program hit this target precisely.
- LU (Loudness Unit): This is a relative unit. One LU is equivalent to one decibel (1 dB). It’s used for making adjustments. For instance, a supervisor might tell a mixer, ‘The dialogue feels quiet, please bring it up by 2 LU.’
- True Peak (dBTP): This measurement is used alongside LUFS. It is a more accurate way of measuring peak levels that catches ‘inter-sample peaks’ which can be missed by traditional peak meters and can cause distortion on some playback systems. Deliverable specifications will always include a maximum True Peak level (e.g., -2 dBTP).
The Impact on Mixing for Film and TV
The shift to loudness normalization has been revolutionary. Mixers are no longer fighting to be the loudest; they are mixing to a standardized target. This has brought dynamic range back to audio. A mix can now have genuinely quiet, subtle moments and loud, impactful moments without the entire track being crushed into a narrow dynamic window. For a film’s soundtrack, this is incredibly important for emotional storytelling. When delivering a mix for Netflix, HBO, or any other major platform, adhering to their specific LUFS and True Peak specification is a non-negotiable technical requirement.