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
Project Background
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
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
CVR Transcript and Tape
2146:29 INT-2 ah once your established inbound
right you're good to what?
Catastrophic
Event
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.
Goldwave Analysis
Goldwave is a digital audio editing program.
Goldwave Analysis
Windowed Fourier Transform
Goldwave Analysis
Windowed Fourier Results
Event
Turbines
Propeller Blade Passage
CVR Noise
Frequency (Hz)
5400 & 10300
105
400
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
Transform Parameters:
• Wo – Effects Wavelet width
• dj – Effects scale width
• mother – Type of Wavelet
Scale Parameters:
• J1 – # of Scales
• So – Base Scale
An Example
Fourier Analysis
Wavelet Analysis of Test Signal
Morlet Wavelet
Wo
Wo
== 6
Wo=
24
24
dj = .25
dj
= .25
dj =
.025
Wavelet Analysis of Test Signal
DOG Wavelet
m=2
dj = .025
Wavelet Display Test
Morlet Wavelet
Wo = 6
dj = .125
Wavelet Code Improvements
• Scale Parameter Equations
• Minimum Scale Size
• Maximum Wavenumber
• Beat Phenomenon
• Edge Effects and Tone Width
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