Re: Harp Tuners

["Tim Moyer - Working Man's Harps" <wmharps@xxxxxxxxx>]

Never argue with the data.

Perhaps one of our other colleagues will weigh in with their observations.
I still *believe* I observe this effect, though I am not above convincing
that it is attributable to some other source.  It is even harder to imagine
that a harmonica chamber wouldn't be immediately filled with air warmed by
breath thus immediately (rather than gradually) making any pitch influence.  

- -tim
www.workingmansharps.com

At 06:53 PM 2/5/03 -0800, Vern Smith wrote:
>
>----- Original Message -----
>From: "Tim Moyer - Working Man's Harps" <wmharps@xxxxxxxxx>
>> .......................... It is a
>> commonly held understanding (though not scientifically described, to my
>> knowledge) that pennywhistles will change pitch as you play them, making
>it
>> necessary to keep them warmed consistently when tuning them (an even more
>> irreversible process than tuning a harmonica).  In this case, it is
>> probably due more the the temperature of the air column inside the
>whistle,
>> where the vibrations oscillate at the desired pitch.
>
>The formula for the velocity of sound in a gas is V = sqrt( k*g*R*t)  Where
>V is velocity;  k,g,R are constants for air; and t is absolute temperature.
>A 40 degF change in temperature is a 6% change in absolute temp.  Taking the
>square root of 1.06 gives 1.03 for a 3% change in sound velocity. This is
>worth about 50 cents worth of pitch change or about 1.25 cents for every
>degree of temp change..
>
>However, it is hard to imagine that a penny whistle would not almost
>immediately be filled with air at body temperature, making the temp of the
>whistle itself irrelevant.  The change in length of the whistle is only 6 or
>7 parts-per-million per degF and would not make a perceptible pitch change.
>
>Vern
>
>
Tim Moyer
Working Man's Harps
wmharps@xxxxxxxxx
http://tymoyer.home.texas.net/WorkingMansHarps/