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

Loudness Measurement

Loudness measurement takes the frequency sensitivity of the human ear to loudness levels into account. There are three types of measurements:

  • Integrated loudness, also called program loudness, establishes the average loudness of an audio piece. This measurement uses a gating method to ignore long periods of silence.

  • Short-term loudness measures the loudness once a second, on an audio block of three seconds. This provides you with information about the loudest audio passages.

  • Momentary loudness measures a range of 400 ms of audio at intervals of 100 ms. This provides you with instantaneous feedback on the loudness.

Loudness Range

The loudness range measurement serves to establish 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 three 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 the quietest remaining audio blocks. This measurement helps you to decide if and how much compression or expansion to apply to the audio.

True Peaks

When a digital signal is converted to an analog signal, 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 four times, while retaining the peak values.

Naming and Units

EBU R-128 proposes the following naming and unit 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 corresponds to 1 dB in the AES-17 scaling.

When WaveLab Elements relates to the EBU R-128 loudness, it uses these units rather than dB.