Re: Harp Tuners

["Vern Smith" <jevern@xxxxxxx>]

- ----- 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