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<DIV><FONT face=Arial size=2><STRONG>Contact =
Ratio</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><BR>Is the ratio between the time =
the hammer
touches the string and the time the wave traveling along the string from =
the
strike point to the bridge and back to the strike =
point.</FONT></DIV><FONT
face=Arial size=2>
<DIV><BR>If this two times are equal, one have a ratio of 1. This means =
that the
hammer moves away from the string as the string wave returns from the =
bridge and
gives therefore the maximum of energy into the first harmonic. This =
contact
ratio is highly dependent of the string tension and of the hammers =
stiffness.
Assuming a smoothed stiffness in the hammer set will show any =
differences in the
scales strike point stiffness. </DIV>
<DIV><BR>Unfortunately strike point stiffness of the strings of =
a key can
not be taken in correlation to contact time (and therefore contact =
ratio) on the
break from bichords to trichords, since the hammers damping loss is =
different if
there are 2 or 3 strings. So any theoretical calculation of contact time =
with
static formulas go far off from whats happen real.</DIV>
<DIV><BR>With the dynamic model of Mensurix one can measure a realistic =
contact
time.<BR>The Reference Graph allows you to make a sound classification =
of two
different instruments.<BR>Or you can use the contact ratio to set your =
string
diameters at the breaks to achieve a better sound balance.</DIV>
<DIV><BR>On the graph below, the Example 1 curve is from a Hamburg grand =
piano,
and Example 2 is from a Vienna grand piano (modern scale). One can see, =
that
around the break the contact ratio of the Hamburg piano (a scale from =
1880) lies
nearly on a straight line indicating a well balanced sound that will =
keep its
line also if the hammers intonation becomes lost in time. A jump at the =
break of
the the contact ratio may be needled out to some amount, but when the =
hammers
intonation has gone, it will return.</DIV>
<DIV><BR>A relative sound classification can be seen in the Graph 2 =
(with
Hamburg as grey curve in reference) directly since around the break and =
the
upper bass region on the Hamburg model the contact ratio is higher =
(produces a
more bass pronounced sound), wheras on the Vienna model has less contact =
ratio
resulting in a more harmonics pronounced sound in the bass region. This =
must not
be a question of quality, but shows the instrument specific sound
characterization.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The blue line in the graph marks the =
break, (on the
keyboard the red marker)</FONT></DIV>
<DIV> </DIV>
<DIV><IMG alt="" hspace=0 =
src="cid:001601c48b96$bf39d490$2dcefea9@BERNHARDNEU"
align=baseline border=0></DIV>
<DIV> </DIV>
<DIV>best regards,</DIV>
<DIV> </DIV>
<DIV>Bernhard Stopper</DIV>
<DIV>more info:</DIV>
<DIV><A
href="http://www.piano-stopper.de/html/mensurix_51.html">http://www.pia=
no-stopper.de/html/mensurix_51.html</A></DIV></FONT></DIV></BODY></HTML>