# Wavelet Analysis of a Cockpit Voice Recorder by ert554898

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```									     Wavelet Analysis
of

Cockpit Voice Recorder Data
Project Responsibilities

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
Catastrophic         right you're good to what?
Event
2146:34 INT-1 oh #.

2146:34 CAM ((sound of altitude alert chime))

2146:35 INT-2 stop one thing at a time.
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             Frequency (Hz)
Turbines             5400 & 10300
CVR Noise                 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 = 6
Wo =
Wo =
24 = .25
24
dj
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

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