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ADR-v2-097 — Mouth-Sound Switch Access (non-verbal acoustic switches + scanning)

Status: Accepted (2026-07-02) · Wave L Context links: wakeword, cmdspotter (few-shot commands), continuum (accessibility), [[adr-011]]

Context

Wave L research (#2) — map short non-speech mouth sounds (pop, click, tongue-cluck, "sh") to discrete switches that drive a scanning selector: "pop" = advance the highlight, "cluck" = select. Distinct from Wake-Word, Few-Shot Command Spotter, and Gesture Chords: this is the switch-scanning AAC paradigm (1–2 signals + a timed scan cursor), the standard access method for people who cannot produce reliable speech at all. Nothing in the set implements scan-and-select. Anchor: Apple Sound Actions for Switch Control / AssistiveTouch (iOS 15, 2021) — ships exactly this (click, cluck, "e", "k", "pop", "sh"…) for non-speaking users with limited mobility.

Decision

Add an opt-in Mouth-Sound Switch Access: [mouthswitch] enabled=false, dwell_s=1.2. Pure cores in mouthswitch/scan.py: classify_mouth_sound(features) → pop | click | sh | None from onset/spectral features, and ScanSelector — a pure timed state machine (tick(now) auto-advances the highlight on a fixed dwell; on_switch("advance"|"select", now) moves or returns the chosen item). The acoustic classifier is the lazy audio extra; the scan cursor + dwell timing (the accessibility-critical part) is pure and testable with a fake clock. OFF by default.

Consequences

  • The switch-scanning access method for non-speaking, severely motor-impaired users.
  • Pure scan cursor + debounce/dwell → fully testable with a fake clock.
  • Distinct from wake-word/command-spotter (scan-and-select vs recognition).
  • Privacy (ADR-011): local audio only.
  • Caveat: single/dual-switch scanning is slower than speech (inherent to the paradigm); off by default.