Research note: /t/ closure leak and burst level

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/research/articulatory-vocal-tract-sources.md

@@ -147,6 +147,8 @@ Re-measure 2026-11-12 on main c0e6b98 (`tools/formant-check/weak_spots.py` over
   peak/centroid /t/ 4172/8729 Hz, /k/ 6984/10218, /p/ 7087/10423 (burst 0.019): /t/ below /k/, the order Chodroff and Wilson 2014 have reversed (t 5216, k 2868, p 2236 Hz). The decision gate said inject. Now a contact whose position has a control surface (made by the first non-labial plosive of a word) injects its burst there: `LadderInjection`, spread over the two cells whose centres bracket the place,
   scaled by cell area over first-cell area (the ladder carries flow waves). /t/ 4008/6681 Hz, /d/ 4008/6693, /k/ 3747/9312 (peak 3747 without the floor too); /t/ is above /k/ by 261 Hz, short of the 2348 Hz of the corpus. Burst window peak /t/ 0.160, /k/ 0.148, /p/ 0.019; closure residue under 0.004. Unscaled, the injection made the closure 30 times louder (outside peak 0.058).
   /p/ and /b/ keep the glottal end and their Faust source byte for byte (`PlaceTableKeepsLabialAndAlveolarPositions`); their burst peak above 1 kHz is 7087 Hz, above /t/, and below 1 kHz it is a 434 Hz low resonance, not the place cue: the labial site is not moved. Below 1 kHz /t/ and /d/ peak at 480 Hz, the same low resonance. Unheard.
+- /t/ closure leak, 2026-11-12 (explicit descriptor, not in the table; /ata/ against /apa/ without burst, closure = 0.2 to 0.65 of the consonant, dB re the mean power of the flanking vowels): the alveolar closure was held at the nasal's 0.03 cm aperture and opened at 0.5, and read -14.3 dB against /p/ -22.1 (the lips seal /p/ whatever the tongue does); the same window with the aperture 0 for the whole gesture, -24.3. A non-labial plosive now holds aperture 0 to 0.65: -24.9 dB (test run) against /p/ -20.4.
+  Its injected burst peaked at 0.76 of the following vowel's peak at the shared gain 0.06 (/b/ 0.19): `TongueStopBurstGain` 0.03 gives 0.39 (0.0438 against 0.1129). Burst spectrum unchanged by the gain: peak 4011 Hz, centroid 5796 Hz, inside 3.5-7 kHz. Not met: /t/ above /p/ in burst peak (/p/ 7087 Hz above 1 kHz, 434 Hz below): the labial burst is still injected at the glottal end, which this branch pins. /k/ closure at the old 0.44 fraction is not sealed (core -15.7 dB). Unheard.
 - Phones the tract cannot make: `WordRender` refuses /t/, /d/, /k/, /l/ with exit 4 (`UNSUPPORTED PHONES (the tract has no gesture for them; nothing rendered): t`); the table holds p b m n s z ʃ ʒ ʍ w and the Story vowels. A direct `phoneme_gesture` on an unknown IPA symbol still falls back to an alveolar approximant (`GestureDescriptor`); not changed here.
 
 Mutations (hand-applied, restored, each run against the named tests): pitch ratio ignored, burst removed, burst not shaped by opening, burst gain x20 (0.06 to 1.2), stress duration ignored,