APU Software

APU Loudness Meter

Loudness range 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.

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 300ms. 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


Choose your operating system to download the latest installer below.

MacOS Windows User Manual

The user manual above is also available on the live docs site.

System requirements: macOS 10.14 (x86, x64, ARM), Windows 10 (x86, x64), OpenGL 3.2.
Supported plug-in types: VST, AU, AAX (Pro Tools 11+).