APU Loudness Meter

APU Loudness Meter is a free loudness analysis plug-in supporting a variety of loudness types and metering modes with clean adjustable visuals. You can monitor in real-time using live history and histogram views, or analyze an entire file to view the overall statistics and histograms.

• Loudness types: LUFS (Momentary, Short-term, Integrated), RMS, Peak, and True Peak.
• Multi-channel: Supports stereo, surround, and Dolby Atmos® formats.
• Channel modes: Split or link channels for flexible metering.
• Visualizations: Live histogram and time-history views with configurable history lengths.
• Statistics: View min, peak, and average as well as LRA and Integrated LUFS.

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

Loudness Types

The APU Loudness Meter can be configured to use any of the following loudness types:

Momentary

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. You can also configure the window duration for finer control over the response time.

Short-Term

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.

Integrated

Integrated is an infinite duration LUFS measurement. K-weighting and channel weighting are applied as with momentary, as well as both relative and absolute gating.

RMS

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.

Peak

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

Credits

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)
• melatonin_blur (blur effects)

Demo video song credits:

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