Wavelet Analysis of a Cockpit Voice Recorder by ert554898


									     Wavelet Analysis

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 Wavelet Theory

•Project Background
•CVR Basics & Recording
•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?
         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             Frequency (Hz)
           Turbines             5400 & 10300
   Propeller Blade Passage          105
          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
dj = .25
dj =
     Wavelet Analysis of Test Signal
                 DOG Wavelet

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

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

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