Source: https://guthlabs.ai/docs/instruments/loudness-unit-lufs-reference-target-checker/
instrument / verified-clean
# Loudness Unit (LUFS) Reference / Target Checker
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Audio, Music, Photography & Color
**Tranche**: tranche-7
**Evidence ID**: t7-083
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The comparison concept is valid, but the instrument needs a documented gain-adjustment sign convention, an explicit pass tolerance, versioned provenance and effective dates for each target, and clearer labeling that these are nominal guidance/reference values rather than universal platform guarantees. Actual LUFS analysis remains out of scope as stated.
### Formula and scope findings
- The gain-adjustment sign is ambiguous: if delta = measuredLUFS - targetLUFS, the gain needed to reach the target is targetLUFS - measuredLUFS, which is the negative of delta.
- The specification does not define a pass/fail tolerance. The vectors below assume pass only when measuredLUFS exactly equals the nominal target.
- The listed Spotify and YouTube values are commonly cited guidance values, not necessarily immutable platform requirements; platform normalization policies and targets may change.
- EBU R128 at -23 LUFS is a broadcast loudness target/nominal reference, not a platform-delivery target.
### Unit assumptions
- LUFS means integrated loudness in LUFS/LKFS-equivalent units; LUFS values are treated numerically as dB-like quantities for differences.
- The gain adjustment is defined here as targetLUFS - measuredLUFS, in dB: a negative value means attenuate and a positive value means increase gain.
- Pass means exact equality to the nominal target because no tolerance was supplied.
- The supplied measured value is already an integrated loudness measurement; this checker performs no audio analysis or LUFS conversion.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
The specification has no division or domain trap, but an extreme finite LUFS input causes the target offset to disappear through floating-point precision, and the instrument does not state finite-range or plausibility validation. The sign of the reported gain adjustment is also convention-dependent unless delta and corrective gain are kept distinct.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"inputs": {
"measured_integrated_lufs": -12,
"target_platform_preset": "Spotify"
},
"expected_outputs": {
"target_lufs": -14,
"delta_measured_minus_target_lufs": 2,
"gain_adjustment_suggestion_db": -2,
"pass": false
},
"reference_data": {
"Spotify_target_lufs": -14,
"source_convention": "widely tabulated platform guidance value; verify current Spotify documentation"
},
"working": "1. Target = -14.0 LUFS from the Spotify table row. 2. Delta = measured - target = (-12.0) - (-14.0) = 2.0 LUFS. 3. Gain adjustment to reach target = target - measured = (-14.0) - (-12.0) = -2.0 dB, so reduce gain by 2.0 dB. 4. Pass test: -12.0 == -14.0 is false."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche7/tranche7-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`