APU Software

APU Loudness Meter

LUFS, True Peak, RMS, Peak

The APU Loudness Meter plug-in is a free dynamic range analysis tool supporting a variety of loudness types (LUFS, True Peak, RMS, Peak). View changes to your audio’s loudness in real-time or get a bigger-picture look with configurable history and histogram views. View both real-time and accumulated statistical information all from one screen.

System requirements: macOS 10.14 (x86, x64, ARM), Windows 10 (x86, x64), OpenGL 3.2.
Supported software formats: Standalone application, VST, AU, AAX (Pro Tools 11+).

Loudness flavors

One of the key features of this meter is its support for a variety of loudness types. You can also choose to split or link channels, which is particularly useful for multi-channel audio formats such as Dolby Atmos®.

The meter can be configured to use any of the following loudness types:


Momentary is a short duration LUFS measurement (400ms), which is useful for processing the audio’s moment-by-moment dynamics. These measurements utilize K-weighting and channel weighting to improve perceptual accuracy.

Momentary LUFS


Short-Term is a longer duration LUFS measurement (3 seconds), which is useful for processing the audio’s large scale dynamics. Given the longer duration, this mode is less responsive than momentary, but it can be useful for analyzing the bigger picture of the audio’s dynamics. K-weighting and channel weighting are applied as with momentary.

Short-Term LUFS


RMS loudness types use a rolling time interval of 150ms by default, which can be adjusted. RMS is a traditional loudness measurement, which is a good first-order approximation of perceived loudness. This mode doesn’t apply K-weighting or channel weighting.


True Peak

True Peak loudness types are similar to traditional peak measurements, but they are more accurate as they take into consideration inter-sample peaks. These measurements use a time interval equal to the configured block size (1ms by default).

True Peak


Peak loudness types are a standard peak circuit, operating on a time interval equal to the configured block size (1ms by default). This mode is doesn’t take into consideration inter-sample peaks.

True Peak

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This software was developed by APU Software, LLC and is available as VST (windows x64/x86, macOS universal), Audio Unit (macOS universal), Pro Tools (windows x64/x86, macOS universal), or Standalone Application. The software libraries below are utilized for portions of the software:

  • JUCE (cross-platform audio and user interface framework)
  • Boost (header-only algorithms)
  • libebur128 (loudness measurements)

Demo video song credits:

  • Annasara - A Lifetime Rolls By, licensed via Audiio.

VST compatible

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