APU Software introduces APU Loudness Contour

[caustik]

APU Loudness Contour is a real-time equal-loudness filter that 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.

 

[jhaider]

How does this work? Can you use it while Airplaying into a modern Mac mini from an iDevice or another Mac?

 

[caustik]

How does this work? Can you use it while Airplaying into a modern Mac mini from an iDevice or another Mac?

There are VST3, Audio Unit, and Standalone application versions. Not sure if Airplay can be used under those scenarios. If Airplay shows up as an input device then you should be able to run it through the standalone version.