Page 79 - The Strad (February 2020)
P. 79
MAKING MATTERS
Figure 1 Results of Croen
2019, measurement 1
(black: ebony #1), 2 (red:
evaluating the qualities of an instrument.
ebony #2), & 3 (blue:
And now we have smartphones with apps Sonowood Scots pine).
that can turn them into ‘audio callipers’,
2 -;9 -2-ধ!£ 9;!;' l mT
;,' =-3£-2 -9 9-+2-)$!2;£@
making them an essential workbench tool. higher in amplitude across
At the 2010 Violin Society of America its range than in states 2
convention I gave a talk describing how to & 3, where the band
£'='£9 !8' !£139; -&'2ধ$!£W
measure the wood properties of Note that each
ngerboards, how to tune the ngerboards measurement shows
changes in peak height
and track B0. is paper (which can be and frequency across the
found at bit.ly/35fe7qP) has detailed whole spectrum.
instructions for tuning as well as a
spreadsheet for creating a personal
database of ngerboards. I had found that Figure 2 Results of Haug
2019: measurement 1
the relationship of the body vibration (B0) (black: Sonowood maple),
to the primary air mode (A0, or A-Zero) 2 (red: ebony), & 3 (blue:
was critical, and I believed that, through Sonowood spruce). Once
again we see changes
repeated tests, I could hear the dierences. across the range,
ere were three key points I learnt: rst, and these are most
pronounced in the two
that I preferred separating A0 and B0 by at
highest frequency bands.
least 25Hz because I felt it enhanced the
focus and power in the low register. Second,
when B0 and A0 were separated by less
than 15Hz, the low register felt spongy and
dicult to play. ird, that I could not get
the results I wanted with every ngerboard.
Although matching the frequencies of
Figure 3 Results of
B0 and A0 is a successful way to lend Benischek 2018:
‘liveliness’ to an instrument, it is measurement 1 (black:
ebony), 2 (red: Sonowood
impractical to maintain. One planing of blacknut). In measurement
the ngerboard can lower B0 by 2–5Hz 2, the B0 peak has moved
depending on the condition of the down in frequency to
split A0. The overall
ngerboard, and successive planings can amplitude goes up slightly
adversely shift the B0/A0 relationship. in the lowest frequency
For this reason, and because the band, but that seems to
8'*'$; $,!2+'9 ;3 ;,'
properties of my ngerboards allow me modes. Note that the
to, I have been tuning B0 below A0. largest change seems
to be occurring in the
Boris Haug and others have been tuning !$3<9ধ$!££@ -1638;!2;
B0 well above A0 – around 300–330Hz, Bridge Hill area (third
also with good results. Choosing a band from the right).
ngerboard blank with higher stiness density, sometimes referred to as the – a conclusion we were pleased to see.
and lower weight allows for tuning to ‘gure of merit’). We chose three violins Although this project represents a small
a higher frequency. We were able to to measure with as many dierent sample, it is interesting that the changes
ngerboard scenarios as time allowed,
aected the instruments broadly, not just
ALL GRAPHS COURTESY JOSEPH CURTIN what we would learn. and soundpost positions. continues to evolve, and further testing
incorporate both tuning strategies into
being careful to keep consistent bridge
our experiment and were eager to see
in the A0 region. Our understanding
We began by measuring 45
will teach us more about the A0/B0
relationship. e next stage will be to
he graphs above show that our
ngerboards (26 alternative materials
and 19 ebony) to compare their properties
apply this knowledge to improve the
subjective observations were
performance of our instruments in
and to calculate the ‘radiation ratio’ (the T consistent with the measurable
calculated speed of sound divided by
FEBRUARY 2020 THE STRAD 77
www.thestrad.com dierences shown in the spectral analyses more predictable ways.
