The paper trains ten independent MAPS LSTM forced aligners, applies order-statistic confidence intervals (2ndβ9th order statistics β 97.85% nominal CI), and evaluates gradient boundary regions on TIMIT and Buckeye American English corpora. Code and data are openly archived on GitHub (github.com/maetshju/maps_ci_analysis) and Zenodo (10.5281/zenodo.15571293) ().
Step 1 β Reproduce ensemble alignment. Load the ten pretrained MAPS LSTM models from the Zenodo archive. For each utterance in TIMIT and Buckeye test splits, run forced alignment independently in each model, linearly interpolate boundaries within each model, then take the per-boundary median across ten models as the point estimate and the 2nd/9th order statistics as the CI bounds. Report mean and median absolute error against reference transcriptions ().
Step 2 β Segment-ambiguity analysis. Group boundary-region widths by bisegment category pairs (e.g., vowelβvowel, affricateβfricative, stopβvowel). Compute median widths and empirical CDFs per category to confirm that ambiguous sequences yield wider uncertainty bands ().
Step 3 β Calibration audit. The reported containment of only 34.06% against a nominal 97.85% CI reveals severe miscalibration β the ensemble measures model-function uncertainty, not phonetically true boundary ranges. A key extension is to recalibrate via conformal prediction split by corpus to achieve valid empirical coverage ().
Step 4 β Cross-corpus generalization. TIMIT (read speech) yields lower errors than Buckeye (conversational speech), confirming domain sensitivity. Extend by testing on non-American-English corpora (e.g., Mandarin, Dutch child speech) to probe generalizability beyond the training distribution ().
Known blindspots: No statistical significance tests for ensemble improvement; no comparison with human annotator inter-rater uncertainty; Praat TextGrid format cannot natively encode overlapping or gradient boundaries; ensemble inference is ~10Γ slower; single-author study without independent replication.
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