1. Processing Sound Files
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 .
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

5. Conversion Need data in *.wav format for digital post-processing
Use conversion utility such as:
Online conversion:
Download freeware audio editor:

6. Matlab Utility
vibrationdata > Miscellaneous > Sound File Editor > 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 Hz
N2 Core Hz
Engines were at 85% power for this recording.
vibrationdata > FFT input one of the sound channels