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MMD > Archives > May 2013 > 2013.05.26 > 05Prev  Next

Player Piano Valve Design Parameters
By John A. Tuttle

Hi All,  Regarding Douglas Heckrotte's comment: "I had thought then
that the volume of air that it took to allow the pouch to rise would
be made available by a vacuum pulse traveling down the tube."

Actually, it's a pulse of atmospheric air pressure that's traveling
down the tube.  However, I also believe the pulse is traveling at
around 700 mph (the speed of sound).  That's about 1025 feet per
second.  So, the difference in time with a 2-foot piece of tubing and
a 30-foot piece would be 0.029268 second - 0.009512 second, or 0.019756
second, which is about 20 milliseconds.  By comparison, the average
'blink of an eye' is 300-400 milliseconds.

So, it's doubtful that the human eye or the human ear could actually
detect the difference in start times.  It's actually more likely
that it would be almost impossible to lift two fingers off of two
holes at exactly the same moment in time.  I personally found this
out when recording music on a digital piano, and it was set to detect
differences as slight as a 1/128th note at 120 beats per minute.
That's 15 milliseconds.  As hard as I tried, I could not consistently
activate or deactivate two notes at the same exact time.  But, at no
time could my ears detect the errors.

John A Tuttle
Brick, New Jersey, USA

(Message sent Sun 26 May 2013, 17:15:00 GMT, from time zone GMT-0400.)

Key Words in Subject:  Design, Parameters, Piano, Player, Valve

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