Cents / Pitch Deviation Calculator mechanism

Model scope

Formula is correct conditional on positive, same-unit frequencies and a signed-output convention. Verdict remains NEEDS_REVIEW because the spec does not define whether deviation is signed or absolute, does not specify frequency units, and does not state the positive-input constraint.

• The formula is standard for signed cents when f1 is the measured frequency and f2 is the reference frequency.
• The spec does not state whether the output should be signed or an absolute deviation; reversing f1 and f2 changes the sign.
• The valid input domain is unspecified: both frequencies must be strictly positive and expressed in compatible units.

Units and conventions

• The frequency ratio must be dimensionless, so f1 and f2 must use the same unit before division.
• The test vectors use Hz unless a unit is explicitly provided; 1 kHz must be converted to 1000 Hz before applying the formula.
• Cents are a dimensionless logarithmic interval; 100 cents equals one equal-tempered semitone and 1200 cents equals one octave.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "f1": 440,
    "f2": 440,
    "unit": "Hz"
  },
  "expected_outputs": {
    "cents": 0
  },
  "working": "f1/f2 = 440/440 = 1. log2(1) = 0. cents = 1200 × 0 = 0 cents."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The formula produces undefined results for zero frequencies, but the specification does not state positive-frequency validation or rejection behavior. It also leaves the sign/order convention to the interface beyond the formula notation, creating a plausible +1200 versus -1200 interpretation.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json