Special Topic 1 - PowerPoint PPT Presentation

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Special Topic 1

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... http://www.zamzar.com/ Download freeware audio editor: ... crj900.wav - noise inside aircraft ... input one of the sound channels Each turbofan engine ... – PowerPoint PPT presentation

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Title: Special Topic 1


1
Special Topic 1
  • Processing Sound Files
  • The most interesting sounds are those which have
    sine tones

2
Record Sound with Your Device
3
For Android Users
Allows sound recordings to be transferred in
.ogg format via Email. Similar apps appear to
be available to iPhone Apple Devices
4
Audio File Formats
There are many types of formats. Common ones
are .mp3 - MPEG Layer III Audio - compressed
format - popular for CDs .ogg - Ogg Vorbis -
open source - compressed format - Archos and
Samsung .wav - large file sizes, convenient
for conversion to ASCII text
http//en.wikipedia.org/wiki/Audio_file_format
5
Conversion
Need data in .wav format for digital
post-processing Use conversion utility such as
  • Online conversion
  • http//www.zamzar.com/
  • Download freeware audio editor
  • http//audacity.sourceforge.net/

6
Matlab Utility
vibrationdata gt Miscellaneous gt Sound File Editor
gt Read wav File Read wav file then Export to
Matlab (one or two channels)
7
CRJ-900 Cabin Noise Example
8
Sample Sound File, Two Channels
Read into Matlab. Then Export to Workspace
File crj900.wav - noise inside aircraft cabin
due to engines, etc.
9
Fast Fourier Transform
Each turbofan engine has two rotors. N1 Fan -
104 Hz N2 Core - 252 Hz Engines were at 85
power for this recording.
vibrationdata gt FFT - input one of the sound
channels
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