APU Software Loudness Contour v4.2.4 x64 UB Win MacOS

APU Loudness Contour is a real-time equal-loudness filter plugin for music producers and audio engineers who want to shape frequency balance according to human perception. It provides multiple standardized contours—ISO 226 (2003 and 2023), Fletcher-Munson, K-weighting, A/C-weighting, ECMA-418, and ITU-R 468—each normalized to 0 dB at 1 kHz. A dedicated contour weight parameter lets you scale the response positively or negatively, with 0% giving a flat response and negative values inverting the contour. For ISO 226 and Fletcher-Munson curves, you can adjust the reference level from 20 dB SPL to 120 dB SPL with smooth interpolation between phon curves. The plugin offers both linear phase and minimum phase filter types. Built-in makeup gain compensation, calibrated via pink noise LUFS measurements, offsets the contour response automatically, and an additional output gain allows manual fine-tuning. A comprehensive real-time spectrum analyzer includes configurable FFT sizes, window types, bucket widths, and time averaging, with linear, logarithmic, or musical note frequency scales, auto-zoom, and custom dB range. Ideal for mixing and mastering with perceptual awareness.