Loudness Meter

About Loudness Metering

Peak and RMS level metering don't necessarily match what we perceive as loudness very well. Short term RMS levels are related to loudness, but the sensitivity of the human auditory system is frequency dependent and that needs to be taken into account when measuring perceived loudness. The EBU R128 (based on the ITU-R BS.1770) recommendation defines a more suitable way of measuring loudness and deals with important issues such as how to react to loudness changes over time and how to measure loudness in multichannel audio. These two recommendations are becoming increasingly popular and are important to ensure a consistent listening experience when switching between audio tracks, television channels, radio programs and similar. Most music streaming providers and broadcasting organizations now specify loudness requirements that content providers need to adhere to.

Note: The Normalize processor in Acoustica (see Volume > Normalize...) supports EBU R128 / ITU-R BS.1770 as well and lets you set a target integrated loudness level in LUFS.

The Loudness Meter in Acoustica

Acoustica has loudness metering built in that follows the EBU R128 and ITU-R BS.1770 recommendations. You can enable and disable the meter using View > Analyzers > Loudness Meter.

The loudness metering in Acoustica showing the loudness curves from the last 30 seconds of output audio along with the current momentary loudness, short-term loudness, integrated loudness and the loudness range as defined by the EBU R128 recommendation.

There are four different loudness measures defined by the EBU R128 recommendation and all of these are displayed in the loudness meter in Acoustica:

• Momentary (LUFS)

The momentary loudness is calculated based on audio from the past 400 milliseconds and is visualized with a yellow curve in the loudness history graph. The maximum momentary loudness since start of playback is displayed in parenthesis.

• Short-term (LUFS)

The short-term loudness is calculated based on audio from the past 3 seconds and is visualized with a blue curve in the loudness history graph. The maximum short-term loudness since start of playback is displayed in parenthesis.

• Integrated (LUFS)

The integrated loudness is a measurement of the loudness of a complete audio track or program. Absolute and relative gates are used to avoid silent or very soft periods from affecting the loudness measurement. The integrated loudness is visualized with a white or red horizontal line in the loudness history graph. The indicator is white when the integrated loudness is below the target level and red if it is above. You can set the target level in the analyzer settings (see description below).

• Loudness Range (LU)

The loudness range is a measure for the loudness variance over time. Large changes in loudness levels over time will result in an increased loudness range.

Acoustica also indicates the illegal loudness range with a red background color in the loudness history.

Loudness Meter settings

You can change the settings by clicking the cog icon in the bottom left corner of the loudness meter. The following window will appear:

The Loudness Meter Settings lets you select the target level, minimum level, and maximum level in LUFS.