Vibrationdata Special Topic 1 Processing Sound Files Matlab

Vibrationdata Special Topic 1 Processing Sound Files Matlab & Python The most interesting sounds are those which have sine tones 1

Record Sound with Your Device Vibrationdata 2

For Android Users Vibrationdata Allows sound recordings to be transferred in *. ogg format via Email. Similar apps appear to be available to i. Phone & Apple Devices 3

Audio File Formats Vibrationdata There are many types of formats. Common ones are: *. mp 3 - 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 4

Vibrationdata 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/ 5

CRJ-900 – Cabin Noise Example Vibrationdata 6

Matlab Utility Vibrationdata Sample file: crj 900. wav vibrationdata > Miscellaneous > Sound File Editor > Read wav File Read wav file then Export to Matlab (one or two channels) 7

Sample Sound File, Two Channels Vibrationdata Read into Matlab. Then Export to Workspace File: crj 900. wav - noise inside aircraft cabin due to engines, etc. 8

Matlab Fast Fourier Transform Vibrationdata Each turbofan engine has two rotors. N 1 Fan - 104 Hz N 2 Core - 252 Hz Engines were at 85% power for this recording. vibrationdata > FFT - input one of the sound channels 9

Python Utility Vibrationdata Sample file: crj 900. wav vibrationdata > Miscellaneous > Sound File Editor > Read wav File Read wav file then Save to Text (one or two channels) 10

Python Fast Fourier Transform Vibrationdata vibrationdata > FFT - input one of the sound channels 11