EBU Loudness Standard R-128

The EBU loudness recommendation R-128 establishes well-defined methods to measure loudness, dynamics, and peak values, and also defines reference values to achieve for these measurements. Though the reference values are intended for the broadcast world, the measurement methods are helpful in any application dealing with audio and loudness control.

WaveLab Cast supports these audio measurements in many places, for metering, audio analysis, and processing.

Loudness Measurement

This method takes into account the frequency sensitivity of the human ear to loudness levels. There are 3 types of measurements:

  1. Integrated loudness, also called program loudness: this reports how loud an audio piece is, on average. This measurement uses a gating method to ignore long periods of silence.

  2. Short-term loudness: this measures the loudness every 1 second on an audio block of 3 seconds. This gives information about the loudest audio passages.

  3. Momentary loudness: every 100 ms, a range of 400 ms of audio is measured. This gives instantaneous feedback about the loudness.

Loudness Range

This measures the dynamics of the audio signal. It reports the ratio between the loudest and the quietest (but non-silent) sections. The audio is divided into small blocks. There is one audio block every second and each block lasts 3 seconds (analyzed blocks overlap).

The top 10% of the quiet blocks and the top 5% of the loud blocks are excluded from the final analysis. The calculated loudness range is the ratio between the loudest and quietest remaining audio blocks. This measurement helps to decide if and how much compression or expansion can or should be applied to the audio.

True Peaks

When a digital signal is converted to an analog signal, the EBU R-128 recommends measuring an estimation of the real peaks, rather than relying on digital peaks, to avoid clipping and distortion. This is accomplished by over-sampling the signal 4 times and retaining the peak values.

Naming and Units

The EBU R-128 proposes naming and units conventions:

  • A relative measurement, such as a value relative to a reference level: “LU” as “Loudness Unit” (1 LU is 1 dB).

  • An absolute measurement, “LUFS” as “Loudness Unit Full Scale”. 1 LUFS can be understood as 1 dB in the AES-17 scaling.

When WaveLab Cast relates to the EBU R-128 loudness, these units are used rather than dB.