Title: Special Topic 1
1Special Topic 1
- Processing Sound Files
- The most interesting sounds are those which have
sine tones
2Record Sound with Your Device
3For Android Users
Allows sound recordings to be transferred in
.ogg format via Email. Similar apps appear to
be available to iPhone Apple Devices
4Audio 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
5Conversion
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/
6Matlab Utility
vibrationdata gt Miscellaneous gt Sound File Editor
gt Read wav File Read wav file then Export to
Matlab (one or two channels)
7CRJ-900 Cabin Noise Example
8Sample Sound File, Two Channels
Read into Matlab. Then Export to Workspace
File crj900.wav - noise inside aircraft cabin
due to engines, etc.
9Fast 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