Professional Metering

What It Does

Meters are measurement tools that let you see what your audio is doing without changing it. They sit alongside your signal chain, tapping into the audio at key points to show you levels, loudness, and how much processing is being applied -- but they never alter the sound passing through.

TabDSP provides professional-grade metering at every stage of the signal chain: input levels, per-module gain reduction, output levels, LUFS loudness, and true peak measurement. Together, these meters give you the same measurement capabilities found in professional mastering DAWs and broadcast facilities.

Global Meter Section

The global meter bar sits below the module chain and spectrum analyzer canvas, providing an at-a-glance summary of levels and processing across the entire signal chain. It is organized into two rows.

Top Row: Processing Meters

These five meters show signal level and gain reduction at each processing stage:

• IN -- Input level after the input gain control, displayed as independent L/R stereo bars with individual peak hold markers. Shows the signal strength entering the processing chain. Green bars indicate healthy levels; approaching 0 dBFS means the input is hot.
• EQ -- Bipolar gain change from the equalizer. Shows how much the EQ is boosting (positive, green) or cutting (negative) the signal. A reading near 0 dB means the EQ is making minimal overall level change.
• MB -- Maximum gain reduction across all multiband compressor bands. Shows the deepest GR value from whichever band is compressing the hardest. Purple color-coded to match the multiband module.
• COMP -- Single-band compressor gain reduction. Shows how much the compressor is attenuating the signal. Orange color-coded. Values of -3 to -6 dB are typical for moderate compression.
• LIM -- Limiter gain reduction. Shows the brickwall limiter actively clamping peaks. Red color-coded. Occasional flickers of -1 to -3 dB are normal; sustained deep reduction means the signal is too hot for the ceiling.

Bottom Row: Output and Loudness

• OUT -- Output level after the limiter and master gain, displayed as independent L/R stereo bars with individual peak hold markers and a ceiling indicator line. This is the final signal leaving TabDSP. Should never exceed the limiter ceiling when the limiter is enabled.
• LUFS -- Integrated loudness measurement following ITU-R BS.1770-4. Shows the overall perceived loudness of the program material. See the LUFS Metering section below for full details.

Peak Hold Markers

Each level meter bar (IN L, IN R, OUT L, OUT R) displays its own peak hold marker -- a thin line that holds at the highest recent peak for approximately 1 second before releasing. This lets you catch transient peaks that would otherwise flash by too quickly to read. Since each stereo channel has its own marker, you can identify channel imbalances at a glance.

LUFS Metering

LUFS (Loudness Units Full Scale) measures perceived loudness rather than raw signal level. Two signals can have identical peak levels but very different perceived loudness -- LUFS captures that difference. It is the global standard for loudness measurement in streaming, broadcast, and podcast production.

Three Measurement Windows

• Momentary (M) -- 400ms sliding window. Reacts quickly to changes. Useful for spotting loud passages in real time. Fluctuates constantly during playback.
• Short-term (S) -- 3-second sliding window. Smoother than Momentary. Shows the loudness trend over a few seconds. Good for comparing sections of a song or program.
• Integrated (I) -- Measures the entire program from start (or last reset) to now. This is the number that streaming platforms and broadcast standards refer to. Uses gating to ignore silence and very quiet passages that would skew the result.

Reset Button

The Integrated (I) measurement accumulates over time. Press the Reset button to clear it and start a fresh measurement. Use this when you want to measure a specific section: reset at the start of the section, let it play through, and read the Integrated value at the end.

Target Values by Standard

Different platforms and standards require different loudness targets:

• -14 LUFS: Spotify, YouTube, Tidal (standard streaming), Spotify Podcasts
• -16 LUFS: Apple Music, Apple Podcasts
• -23 LUFS: EBU R128 (European broadcast)
• -24 LUFS: ATSC A/85 (US broadcast), NPR / PRSS, ARIB TR-B32 (Japan)

Peak and True Peak

Sample Peak

Sample peak is the highest absolute value among the digital samples in your audio. It tells you the loudest discrete sample value. This is what a standard level meter shows. If a sample peak reaches 0 dBFS, the signal has hit the maximum value the digital format can represent.

True Peak

True peak accounts for what happens between samples. When a DAC reconstructs the analog waveform from digital samples, the interpolated curve between samples can exceed the value of any individual sample. These inter-sample peaks can cause clipping on consumer devices even when the sample peak reads below 0 dBFS.

True peak is always equal to or higher than sample peak. The difference between the two reveals how much inter-sample overshoot your audio contains.

True Peak / Sample Peak Mode

The limiter panel provides a cycle button that switches between two peak detection modes for the PRE and POST stereo meters:

• True Peak mode: Displays both sample peak (cyan bar) and true peak (orange bar) simultaneously. True peak uses 4x polyphase oversampling to detect inter-sample peaks. When the orange bar reads higher than the cyan bar, your audio contains inter-sample peaks -- this is common and expected.
• Sample Peak mode: Displays sample peak only (cyan bar). Shows the highest discrete sample value without inter-sample interpolation.

Click the button to cycle between modes. The button text updates to show the current active mode ("True Peak" or "Sample Peak").

PRE/POST Stereo Meters

The limiter canvas displays stereo meters in two sections:

• PRE (before limiter): Shows L/R input levels entering the limiter. Peak hold markers indicate the highest recent value.
• POST (after limiter): Shows L/R output levels leaving the limiter. An orange ceiling marker indicates where limiting begins. Output levels should never exceed this marker when the limiter is enabled.

L/R Stereo Metering

The IN and OUT meters display independent left and right channel levels as separate stereo bars. Each channel has its own peak hold marker, giving you precise visibility into the stereo image of your audio at the input and output stages.

Input Stereo Meters

The IN meter shows two bars (L and R) representing the left and right channel levels after the input gain control. Each bar has its own peak hold marker. A mono source will show identical levels on both bars; a stereo source will show the natural level differences between channels.

Output Stereo Meters

The OUT meter shows two bars (L and R) representing the left and right channel levels at the final output stage, after the limiter and master gain. A ceiling marker line overlays both bars, showing where the limiter ceiling is set. Output levels should never exceed this marker when the limiter is enabled.

LUFS Stack

The LUFS Stack is an expanded loudness analysis panel that sits below the global meter section. It provides three independently collapsible sub-components for detailed loudness measurement, target validation, and visual history -- bringing broadcast-standard loudness analysis capabilities to the browser.

Meter Sub-Component

The top section of the LUFS Stack displays three horizontal bar meters with numeric readouts:

• M (Momentary) -- 400ms sliding window loudness. Reacts quickly to level changes. The bar fill and numeric value update in real time.
• S (Short-term) -- 3-second sliding window loudness. Provides a smoother view of the loudness trend.
• I (Integrated) -- Cumulative loudness from the start of analysis (or last reset). This is the number streaming platforms and broadcast standards reference.

Each bar includes a visual fill that scales proportionally to the measurement value, alongside a numeric readout in LUFS. The meter sub-component can be independently collapsed via its own toggle button.

Target Validator

The middle section compares your current measurements against the target values from the active compliance preset. It operates in three modes, selectable via buttons:

• I (LUFS-I Target) -- Compares the Integrated LUFS measurement against the preset's loudness target. The display turns blue when the measurement is within ±0.1 dB of the target, indicating compliance.
• LRA (Loudness Range) -- Shows the Loudness Range measurement. See LRA below for details.
• TP (True Peak) -- Compares the measured true peak against the preset's ceiling. The display turns red if the true peak exceeds the ceiling.

The delta toggle button (shown as a triangle icon) reveals the numeric difference between the current measurement and the target value. This is useful for seeing exactly how far your program material is from compliance.

The Target Validator automatically inherits its target values from the active compliance preset -- there is no separate target configuration. Select a compliance preset in the limiter panel (e.g., "Spotify", "EBU R128", "NPR / PRSS") and the Target Validator adopts those targets immediately.

Histogram

The bottom section provides a canvas-based scrolling visualization of loudness over time. Two overlapping traces show:

• Green fill: Momentary loudness (behind)
• Blue fill: Short-term loudness (in front)

The histogram operates in two modes:

• SCROLL (default) -- Shows the last 10 literal seconds of loudness data, scrolling right-to-left as new data arrives. Time scale labels along the bottom show 0s through 10s.
• FIT -- Scales the entire analysis history to fit the canvas width. As the analysis runs longer, the time scale compresses to show the full picture. Time zone markers update as elapsed time grows.

The histogram sub-component can be independently collapsed. The histogram only records data while analysis is active (see Analyze toggle below).

Controls

• Analyze -- An explicit start/stop toggle that controls histogram recording and Integrated loudness accumulation. Momentary and Short-term values continue updating regardless of the Analyze state, but the histogram only records and the Integrated value only accumulates while Analyze is active. Click to start analysis; click again to stop.
• Reset -- Clears all LUFS measurements (Momentary, Short-term, Integrated), the histogram canvas, and the Target Validator readings. Use this to begin a fresh measurement of a specific passage.
• Collapse chevron -- Collapses the entire LUFS Stack panel. Each sub-component (Meter, Target, Histogram) also has its own collapse toggle for granular control over what is visible.

LRA (Loudness Range)

Loudness Range (LRA) measures the dynamic range of your program material in LU (Loudness Units). It tells you how much the loudness varies over the course of the measurement -- from the quietest meaningful passages to the loudest.

How LRA Is Computed

LRA is computed from the distribution of Short-term loudness values, following EBU Tech 3342. After gating out silence and very quiet passages, the range between the 10th percentile and the 95th percentile of the remaining Short-term values gives the LRA in LU. This excludes extreme outliers (the very loudest transients and the quietest non-silent passages) to give a robust measure of typical dynamic variation.

Interpreting LRA Values

• 3-5 LU: Heavily compressed material. Typical of loudness-war-era masters, EDM, and heavily processed podcasts. Very little dynamic variation.
• 5-10 LU: Moderate dynamics. Common for pop, rock, and well-produced podcasts. Comfortable for most listening environments.
• 10-15 LU: Wide dynamics. Typical of jazz, acoustic music, and film dialogue. May require a quieter listening environment.
• 15-20+ LU: Very dynamic material. Classical music, film scores, and uncompressed live recordings. Wide swings between quiet and loud passages.

LRA is available in the LUFS Stack's Target Validator when LRA mode is selected. It requires the Analyze toggle to be active for accumulation.

Gain Reduction Visualization

Each dynamics processing module reports its gain reduction (GR) in real time. GR tells you how much the processor is turning down the signal at any given moment. Understanding GR is essential for setting dynamics parameters effectively.

Per-Module GR Meters

Each dynamics module has a dedicated GR meter, color-coded for instant identification:

• Multiband Compressor (purple): Shows the maximum GR across all active bands. The MB meter in the global bar reflects whichever band is compressing the hardest at that moment.
• Single-Band Compressor (orange): Shows the overall compressor GR. This is the straightforward difference between what the compressor would have output at unity gain and what it actually outputs.
• Limiter (red): Shows the brickwall limiter's GR. The limiter canvas also displays a GR waveform -- a red gradient fill from the 0 dBFS reference line downward, showing the shape and depth of limiting over time.

Interpreting GR Values

Gain reduction is expressed in negative dB. Typical ranges for different processing intensities:

• 0 to -3 dB: Light, transparent processing. Suitable for gentle leveling and mix bus glue.
• -3 to -6 dB: Moderate processing. Standard for vocal leveling, drum bus compression, and general dynamics control.
• -6 to -12 dB: Heavy processing. Audible compression character. Used intentionally for effect or aggressive leveling.
• -12 dB and beyond: Extreme processing. The processor is working very hard. Check whether input levels or thresholds need adjustment.

Mini-Meters on Module Blocks

Each module block in the draggable chain displays a compact GR mini-meter. These provide a quick visual check of processing activity without needing to open the full parameter panel. The mini-meters use the same color coding as the global meter bar (purple for multiband, orange for compressor, red for limiter).

Parameter Reference