OX2 ENGINE SOUND
Hear the OX2 engine as it sounded running at 655 RPM on the dynamometer during the November 20, 2001 demonstration at Carroll Shelby Enterprises. The sound sample is about 4 1/2 seconds long, but will take a little time to download. It is best heard if you set your media player playback option to "Repeat forever". With Windows Media Player, click on the Windows Media Player window and select "Options". Then click the "Playback" tab and click on "Repeat forever".
Compare the previous sound sample with the 15 second sample of the stand-alone, propane-powered OX2 engine at 368 RPM recorded during the December 15, 2009 demonstration at Carroll Shelby Enterprises. Much quieter. That's John Luft in the background saying, "Look at that. We can actually carry on a conversation."
Calculating OX2 Engine RPM By Ear
Do you ever wonder if you have a recording of a running OX2 engine, what is its RPM? Or wonder how the OX2 engine would sound, say at 1650 RPM? It's simple to calculate the RPM if you have a piano or other musical instrument handy (or have "perfect pitch"). Just match the OX2 engine fundamental pitch to the piano key pitch.
The OX2 fires each of 8 cylinders twice per revolution, 2 cylinders paired together at a time, so that's 8 paired firings or cycles per revolution. If you know the frequency of the piano key in Hertz or cycles per second, then you can calculate the RPM with the following formula:
RPM = piano key frequency (Hz) x 60 sec/min / 8 cycles/revolution
You can use the following table to get the frequencies of the piano notes:
Music Calculator
A western twelve tone equal temperament reference table in hertz. C4 is middle C.
http://www.musiccalculator.com/twelve-tone-equal-temperament-table.html
A western twelve tone equal temperament reference table in hertz. C4 is middle C.
http://www.musiccalculator.com/twelve-tone-equal-temperament-table.html
The fundamental pitch of the 5 second Nov. 20, 2001 OX2 sample on the dyno is slightly higher than F2 (F two octaves below middle C) or just above 87.307 Hz. The fundamental pitch of the 15 second OX2 sample from the Dec. 15, 2009 meeting oscillates above and below G1 (G three octaves below middle C) or about 48.999 Hz.
87.307 x 60 / 8 = 654.8+ RPM on the dyno
48.999 x 60 / 8 = 367.5+/- RPM at the Dec. 15, 2009 meeting
The fundamental frequency and pitch of the OX2 engine at 1650 RPM would be:
1650 x 8 / 60 = 220 Hz or A3 (A below middle C.)
