Wavelet Analysis of Cockpit Voice Recorder Data

Wavelet Analysis of

Cockpit Voice Recorder Data

Project ResponsibilitiesTeam Leader

Digitize CVR Data, Develop Test Signals

Project ResponsibilitiesCode Developer

Develop Wavelet source code

Project ResponsibilitiesResearch

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.

EventTurbines

Propeller Blade PassageCVR Noise

Frequency (Hz)5400 & 10300

105400

Goldwave Analysis

Final portion of CVR recording

Integral Transformation Theory

What is it?

Transforms a function from one space to anotherdepending on the transfer function.

The Fourier Transform

Signal processing tool that takes asignal 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 = 6dj = .25

Wo = 24

dj = .25

Wo = 24

dj = .025

DOG Wavelet

Wavelet Analysis of Test Signal

m = 2dj = .025

Wavelet Display Test

Wo = 6dj = .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 Wavenumber5 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