Cockpit Voice Recorder (CVR) Configuration zUnused channel acts as vibration transducer

Insulator Inner Conductor Outer Jacket Outer Shield Frictional forces generated at the boundary between the inner conductor and outer shield due to cable vibration strips off free electrons, creating time dependent current that can be measured. The Triboelectric Effect

Demonstration of Triboelectric Effect Twisted pair wire forming an open-circuit with one end connected to an oscilloscope - Wire vibration excited by running thumb-nail over twisted-wire outer insulation.

Jet Turbine Signals from CVR Silent Track Generated by Triboelectric Effect

Red spikes indicator of engine-truss damage Example of Health Monitoring Signature

Laboratory Test Subject: StarLite Aircraft

Current Testing zMount twisted pair wires on StarLite fuselage zUse signal analyzer to obtain data zTake data while tapping aircraft with instrumented hammer zTake data while shaking aircraft to impose background noise level

Impulse Hammer Tests by Impacting Engine-Truss Joint Impulse Hammer Test Wire

Impact Signature Wire Response Impact Hammer Response of Twisted Pair Wire Undisturbed Aircraft

Impact Hammer Response of Twisted Pair Wire Aircraft Undergoing Random Vibrations Impact Signature Wire Response

Conclusions zImpacts induce significant voltages in twisted pair wire zImpact output is visible above background noise yElectrical noise yAircraft vibration zWire amplitude and phase responses are very flat over frequency bandwidth from 600 Hz to 6 kHz