APU Software

Loudness Leveler

Keep vocals and dialog at a consistent level

Sale price $30.00 one-time · Regular price $40.00

APU Loudness Leveler keeps vocals, dialog, and other audio at a steadier level without having to ride every phrase by hand. Set a target loudness and tolerance, then choose how quickly it should adjust the gain. Use it on individual tracks, podcasts, streams, or complete mixes.

Timing modes range from fast gain riding to slower short-term leveling, with an RMS option for more traditional level detection.

Set limits on gain changes, use guard modes to hold correction around transients and tails, or control leveling from a sidechain. Detector EQ changes which frequencies drive the response, and a built-in limiter handles output peaks. Predictive low-latency modes are available when you need to avoid look-ahead delay.

You can also learn a fixed gain correction from a full pass, or use a secondary target for sidechain-triggered changes and quiet passages.

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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+).

Timing Modes

Timing modes select the loudness measurement and its time window. Shorter windows follow brief changes more closely; longer windows smooth the response over more audio.

Tight

Tight uses a 25 ms window with LUFS weighting. It is the fastest mode, suited to following short notes and rapid changes in level.

Focus

Focus uses a 100 ms window with LUFS weighting. It responds quickly while smoothing over more of the signal than Tight.

Present

Present uses the standard 400 ms Momentary LUFS window. It’s a useful starting point for general leveling when you don’t need the faster response of Tight or Focus.

Deep

Deep uses the 3-second Short-Term LUFS window. It follows longer changes in loudness and reacts less to individual notes or brief peaks.

Traditional

Traditional uses a 300 ms RMS detector without LUFS frequency or channel weighting.

Channel Link

Channel Link chooses whether channels share one gain correction or are leveled independently. Linking keeps their relative levels intact; splitting lets the leveler correct each channel separately.

Leveling Controls

The Leveling tab sets the target loudness and target tolerance. When the signal moves outside that range, the leveler adjusts gain according to your timing, gain limits, and guard settings.

Tolerance modes define a fixed range where no correction is needed, or use the measured loudness range (LRA) to scale or adapt the correction.
Guard modes hold gain correction outside selected percentile thresholds to avoid boosting tails or cutting transients.
Sidechain modes can engage, disengage, or directly drive the leveler from an external signal.
Low-level handling can keep leveling active, bypass it below threshold, or gate low-level material so ambience and noise are not over-amplified.
Max cut / max boost set limits on how much gain the leveler can remove or add.
Standard timing modes use look-ahead. The low-latency variants predict the response instead of delaying the signal.

Gain Correction

Gain correction learns a fixed offset to bring average or integrated output loudness closer to your target. Choose Average or Integrated, play a representative pass with learning enabled, then lock the result for playback or export.

The learned value is a fixed dB offset added to the normal leveling correction. Your target, tolerance, timing, guard, and limiter settings continue to apply.

Average learns from the mean output loudness over the render.
Integrated learns from integrated output loudness.
Learn / Lock / Reset starts learning, stores the learned value, or clears it back to 0.00 dB.

Dual Targets

Dual targets let you set a second loudness range for sidechain-triggered changes or quiet passages. Each target has its own loudness and tolerance.

Sidechain Engage Trg and Disengage Trg modes switch or blend between targets around the sidechain threshold and knee. Low-Level Target mode blends toward the secondary target when the signal falls below the low-level threshold.

For example, use a narrow primary range for foreground speech and a lower secondary target for quiet background material.
The secondary loudness and tolerance controls are shared by the sidechain target modes and Low-Level Target mode.
The active target zone is shown in the visualization, so you can see which range the Leveler is currently following.

Alternate Weighting

Alternate weighting curves change how much each frequency contributes to the detector. Use them to adjust how strongly bass, midrange, or high-frequency content drives the leveling. Measurements with alternate weighting are no longer standard LUFS measurements.

The screenshots below show the curves in Loudness Contour. The leveler applies them as zero-latency IIR filters in the detector path.

ECMA-418

ECMA-418 uses the outer- and middle-ear weighting curve from the ECMA-418-2 hearing model. It provides an alternative to K-weighting; it does not apply the standard’s full loudness model.

ITU-R 468

ITU-R 468 emphasizes the upper midrange, making the detector more sensitive to sibilance and other high-frequency content.

A-weighting

A-weighting reduces the influence of low frequencies. Use it when you want bass to contribute less to gain correction.

C-weighting

C-weighting is flatter than A-weighting and retains more low-frequency energy in the detector.

Detector EQ

Detector EQ shapes the signal used for loudness detection. Emphasize a frequency range to make it drive more of the gain correction, or reduce low frequencies so rumble has less influence.

Note: The EQ isn't applied directly to the output, but it changes the leveler's gain response. Enable detector EQ monitor to hear the filtered detector signal.

Low-pass and high-pass filters with selectable slopes
Parametric mid band with bell, shelf, or band-pass shapes
Trim and mix controls for gain and blend
Monitor modes to audition the detector path

Limiter

The built-in limiter controls output peaks after leveling. It uses look-ahead to detect Peak or True Peak levels above the ceiling and reduce gain before they arrive.

Credits

Developed by APU Software, LLC with the following libraries:

JUCE (cross-platform audio and user interface framework)
Boost (header-only algorithms)
libebur128 (loudness measurements)
melatonin_blur (blur effects)

Demo video song credits:

Titan Sound - Technology Flow, licensed via PremiumBeat.