Wavelet Analysis of Cockpit Voice Recorder Data

Project Responsibilities Team Leader Digitize CVR Data, Develop Test Signals

Project Responsibilities Code Developer Develop Wavelet source code

Project Responsibilities Research Research Wavelet Theory

Overview Project Background CVR Basics & Recording Theory Wavelet Parameters Silent Track Analysis

Project Background 1991 Beech 1900C Twin Turboprop Accident

Accident Location Project Background

Right engine mount failed Engine separated and struck empennage Aircraft broke apart in flight Recovered CVR with last 30 min of audio Project Background

Engine Mount Location

Accident Animation

Project Goals Digitize CVR recording Isolate tube failure location Develop Wavelet analysis program Perform Wavelet Analysis on CVR data

Digitize CVR Data

2146:29 INT-2 ah once your established inbound right you're good to what? 2146:34 INT-1 oh #. 2146:34 CAM ((sound of altitude alert chime)) 2146:35 INT-2 stop one thing at a time. you're in a bad situation so correct one thing first. CVR Transcript and Tape Catastrophic Event

Goldwave Analysis Goldwave is a digital audio editing program.

Goldwave Analysis Windowed Fourier Transform

Goldwave Analysis Windowed Fourier Results These frequencies match those found by past research.

Goldwave Analysis Final portion of CVR recording

Integral Transformation Theory What is it? Transforms a function from one space to another depending on the transfer function.

The Fourier Transform Signal processing tool that takes a signal and tells us what frequencies are within that signal.

The Wavelet Transform Determines the frequency spectrum as a function of time.

Morlet Wavelet Equations Morlet Wavelet Scaling/Translation Function Wavelet Transform

Triboelectric Effect Frictional motion creates static electricity Aircraft wires vibrate during flight Vibrations generate static electricity CVR records static electricity

Develop Wavelet Computer Code Obtained existing Wavelet code from C. Torrence and G. Compo Created interface allowing use of Wavelet code Experimented with effect of input parameters

Important Input Parameters Wo – Effects Wavelet width dj – Effects scale width mother – Type of Wavelet Transform Parameters : Scale Parameters: J1 – # of Scales So – Base Scale

An Example

Fourier Analysis

Wavelet Analysis of Test Signal Morlet Wavelet Wo = 6 dj =.25 Wo = 24 dj =.25 Wo = 24 dj =.025

DOG Wavelet Wavelet Analysis of Test Signal m = 2 dj =.025

Wavelet Display Test Wo = 6 dj =.125 Morlet Wavelet

Scale Parameter Equations Minimum Scale Size Maximum Wavenumber Beat Phenomenon Edge Effects and Tone Width Wavelet Code Improvements

Scale Parameter Equations Base Scale Size Number of Scales

Minimum Scale Size

Maximum Wavenumber 5 Hz Test Tone

Beat Phenomenon 50 Hz & 52 Hz Tones

Wavelet Analysis 4p Propeller Mode

Wavelet Analysis Right Engine Turbine

Future Work Continue verifying code consistency Obtain controlled triboelectric test data Investigate other crash explanations

Acknowledgements Dr. Ronald Stearman Pete Moss – UT School of Music Chris Garland Javier Fuentealba Marcus Kruger

Questions