[pianotech] was Beginner's calibration question-thermal conductivity

[Zoe Sandell]

Thanks David

Interestingly, I changed my original email from 'feels colder' to 'be'
colder....

Yes, of course, steel is a conductor and carries heat away from the person
touching it... I had a brain fog moment in my initial email


What I was really trying to ask was ... why do techs warm it up in their
pockets/underarm?  To bring it to the correct hz?  If it has been in a 20
degree room already- then...

Thanks again kindly
Zoe


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of David Boyce
Sent: December 29, 2009 4:53 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Beginner's calibration question

I tried to use NIST to calibrate Tunelab, but had misigvings about 
transatlanic phone lines and telephone handsets.

In the end I found this website useful because it has a nice constant 
440Hz tone (which agreed, beatless, with my tuning fork at 20C)

http://www.indiana.edu/~emusic/acoustics/phase.htm

Scroll to the foot of the page to find the 440, 441 and 442 Hz tones.

Steel will not always be colder then room temperature! It cannot be! If 
a steel object has been sitting in a room for a long time, it MUST be at 
the same temperature as the room.
However, it may FEEL colder if you touch it, because your body is hotter 
than room temperature, and heat is passed from your body to the steel 
object more quickly than it passes from your body to the air in the room.

Try with a thermometer:  Have the thermomenter in the room for a while, 
check the temperature, then put the thermometer on a steel object that 
feels cool to the touch (but has also been in the room a good while). 
The temperature will be the same.

Zoe, if your fork really is at the wrong pitch at 20C (check it against 
the  website above), I'd be inclined to buy a new one.

Best regards,

David Boyce

 >My room temp is 20 degrees.  I wondered about the specifics of 
temperature-
 >certainly the manufacturers could not mean that the fork itself is 20
 >degrees and not the room? As steel will always be colder than its
 >surroundings- cannot recall the exact science behind the difference in 
heat
 >conductors.  I guess the underarm trick simply adjusts the fork enough 
to be
 >accurate?

 >I wonder about the fork- I will take mine into a master tech- to do any
 >filing- but this will likely be necessary.