On 8/30/2014 7:54 PM, Ed Sutton via Piano Technicians Guild wrote:
> Relative to previous discussions:
>
> How do the actions of the front duplex string segments (whatever
> those actions may be) become audible sound? What surface of the piano
> is moving to create sound waves, and how does the energy get
> transmitted to that (those) surface(s)?
Ed, you need to start reading the Journal and list postings, and
attending classes in this stuff.
Transverse string vibrations cross the capo by a rocking action,
activating a transverse vibration in the duplex. This vibration then
reflects back through the capo and into the speaking length. If there is
a low partial in the duplex that corresponds to one of the partials in
the speaking length it will reinforce that partial enough to be audible
by the same mechanism that lets you hear the speaking length tone(s).
This is much more likely from a long front duplex (say, 40mm), than it
is from a short duplex (say, 20mm), which is why short duplexes are
quiet. That's pretty much it. Though a very big deal is typically made
of it, invoking conversational molecules, intuition, and tiny pointy
tailed fire breathing demons, it's really extremely simple.
Next, someone will demand to have proof that transverse vibrations cross
capos. I discovered something fun many years ago playing around in the
shop plucking strings before a rebuild tear down. I lifted the damper of
a note in octave 6 and plucked the duplex. The resulting tone was the
fundamental of the speaking length, which I thought was pretty cool.
When I lifted the middle of the duplex segment, the speaking segment
just past the capo dipped down slightly as the string rocked on the
capo. This is exactly how transverse waves cross capos into the duplex.
There is still no documentation or demonstration that longitudinal waves
cross capos, but transverse waves most certainly to.
And Jim I, this is how long front duplexes rob energy from the speaking
length, as they move with a wider excursion, which takes more to drive them.
Ron N
Original Message------
Relative to previous discussions:
How do the actions of the front duplex string segments (whatever those actions may be) become audible sound?
What surface of the piano is moving to create sound waves, and how does the energy get transmitted to that (those) surface(s)?
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Ed Sutton
Editor
Piano Technicians Journal
ed440@me.com
704-536-7926
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