I recently flew from Spokane to Seattle, Washington on an Alaska/Horizon Air Bombardier Q400 aircraft, similar to the one in the above image.
This model aircraft has two Pratt & Whitney Canada PW150A turboprop engines.
I captured the following video during cruise using a Motorola/Android phone (when it was safe for passengers to turn on their portable electronic devices): Audio/Video File
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(Click on image for a better view)
The PW150A engine/propeller rotation rate during takeoff and climb is 1020 RPM, but is throttled back at cruise altitude to 850 RPM, or 14.17 Hz. There are six blades on each engine, so the blade passing frequency is 85 Hz. This frequency and its integer harmonics are clearly visible in the spectral analysis of the audio track.
Here is the time history: Q400.txt – time(sec) & unscaled sound pressure
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See also: Bombardier
– Tom Irvine
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Notes to self so I can remember the processing steps:
Audio track processing
Extract audio: avconv -i input.3gp output.wav
Matlab script: audio_txt.m
Convert video format: http://www.zamzar.com/
The following steps were done in Ubuntu:
Rotate 90 degrees: avidemux
Trim video footage:
avconv -i input.avi -vcodec copy -acodec copy -ss 00:00:09 -t 00:00:21 output.avi