APU Software has released a real-time equal-loudness contour plugin and standalone application for Windows and Mac.
APU Loudness Contour offers precise control over a wide range of perceptual loudness contours, including ISO 226 (2003 & 2023), Fletcher-Munson, K-weighting, A/C-weighting, ECMA-418, and ITU-R 468.
Each contour is normalized to 0 dB at 1 kHz and includes a dedicated contour weight parameter, allowing you to scale the frequency response in both positive and negative directions. A weight of 0% results in a flat response, while negative weights invert the contour. ISO 226 and Fletcher-Munson curves support variable reference levels from 20 dB SPL to 120 dB SPL, with smooth interpolation between phon curves.
The plugin supports both linear phase and minimum phase filter types. Built-in makeup gain compensation is provided per contour and reference level, calibrated using pink noise LUFS measurements. When enabled, makeup gain offsets the entire contour response by the corresponding gain amount. Additional output gain is available for manual fine-tuning.
A comprehensive real-time spectrum analyzer is included, featuring configurable FFT sizes, window types, bucket widths, and time averaging. Frequency visualization can be switched between linear, logarithmic, or musical note scales, with auto-zoom and custom dB range options.
APU Loudness Contour is available for macOS and Windows in VST3, AU and AAX plugin formats for the intro price of $30 USD. A trial version is available.
Additionally, the APU Loudness Series of plugins has been updated to version v3.7.6:
- Switch default theme to APU Default.
- Fix occasional spectrum analyzer glitches (contour).
- Fix stutter on bypass toggle (contour).
- Improve auto range label visibility.
- Initial release (contour).
- Tweak limiter icons for clarity (limiter).
- Minor fixes.
- Fix axis tick count in certain situations.
- Better uniform random number generation for dithered ballistics.
- Double the number of color themes.
- Smooth axis zooming.
- Fix LUFS limiter ceiling offset in certain cases (limiter).
- Fix latency-dependent preset parameters not loading in certain situations.
- Improved axis and text bubble overlay.
- UI Scaling option in Settings tab.
The update is free for registered owners.
More information: APU Software
