Tier 1

The air tube

A sealed half-metre tube of air is the simplest system in which the whole chain — model, instruments, custody and comparison — can be falsified.

Pre-registration v1.2Awaiting hardware

Apparatus

Tube: Rigid, 0.5 m, closed at both ends, small driver at one end
Sensors: Two measurement microphones, flush-mounted, one shared sample clock
Sampling: 192 kHz (frozen floor: 100 kHz)
Environment: 18.0–20.5 °C, 30–60 % RH, logged at the tube

**Table 7.** Frozen predictions.
Observable	Prediction	Pass if within
Speed of sound	343.24 m/s	1 %
Fundamental resonance	343.24 Hz	2 %

**Table 8.** Pre-registration history. Every amendment was sealed before any physical capture and only made the test stricter.
Version	Change
v1	Contract, geometry, predictions and thresholds frozen before any apparatus existed.
v1.1	Sound speed measured on the direct arrival only, so echoes from the end caps cannot bias it.
v1.2	Envelope narrowed to 18.0–20.5 °C; microphone matching ≤ 1 µs required; gain settings bound to calibrations; post-session calibrator check (drift ≤ 0.5 dB).

A failure at this tier stops the program until it is understood. State: frozen, awaiting hardware.