Dept. for Speech, Music and Hearing
Quarterly Progress and
Status Report
Timbre and properties of a
violin
Jansson, E. V. and Niewczyk, B. K. and
Frydén, L.
journal:
volume:
number:
year:
pages:
STL-QPSR
34
4
1993
007-014
http://www.speech.kth.se/qpsr
STL-QPSR 411993
TIMBRE AND PROPERTIES OF A VIOLIN
Erik V. Jansson, Benedykt Niewczyk* , and Lars Fryde'n
ABSTRACT
It has been suggested that the timbre of a played instrument may be perceived between the excitation pulses, once every period of the played string.
By impulse excitation all resonances of a resonator system will be excited.
The resonance vibrations are damped exponentially between every excitation pulse. Thus the sound in the room will consist of damped oscillations
of the dominating resonances of the violin bod)). The excitation pulses may
be regarded as pickets and the decaying resonance vibrations in between
may present the resonant properties of a violin similarly to the vision of a
landscape through a moving picket fence. Results of obtained wave forms
and their relations to the properties of the played violin will be presented.
INTRODUCTION
In this paper some results will be presented from experiments made in 1992 and 1993.
First laboratory experiments were made on the construction of the violin, i.e. with
opening of f-holes and thinning of the top and the back plates of an experimental violin. Secondly, adjustment experiments were made by changing soundpost positions.
Thirdly, relations between violin properties and time history of played tones were
recorded and will be reported on. The vibration properties of the violin were measured
in form of admittance (impulse excitation at top of bridge parallel with the top plate
and electromagnetic pickup by a 0.025 g magnet via an air gap) and the tonal properties were tested by playing. The vibration properties were analysed in the 500 Hz range
and the 1.5-3 kHz range (the "bridge hill" range).
EXPERIMENTS ON CONSTRUCTION
The construction of the violin is sketched in Fig. 1. The f-holes act as free edges and it
was tested how this boundary condition influences the properties of a violin and its
tonal quality (Jansson et al., 1992). Over the left f-hole violin maker's stamps were
glued to "lock" the free inner edges to the outer edge. The stamps were removed in
steps. The frequency responses (admittance at the bridge) with fastened edges and free
edges show a large change in the 500 Hz range but a moderate change in the bridge hill
range, see Fig. 2. In the playing test the removal of the stamps resulted in considerable
improvement, especially with the removal of the stamps affecting the longitudinal
stiffness (this also applies to the frequency responses). The result indicates that the
crossgrain cutting of the f-holes is the most important.
* Permanent address: Pracownia lutnicza, 61-776 POZNAN, ul Wozna nr 6, Poland
STL-QPSR 411 993
Fig 1. Construction of the
violin. TP marks top plate,
F left fhole, SP soundpost, and BP back plate.
LEFT
F-HOLE
LOOCKED
~.
1
I
I
I
I
I
l
I
l
Log
200
I
1
Hz
5k
BOTH
F-HOLES
FREE
200
I
I
I
I
I
I
1
I
Log Hz
5k
I
Fig. 2. Frequency responses (level) of violin with left f-hole edges "locked" with stamps and
free, respectively.
The thickness of the top and back plates are major parameters for the violin maker.
An experimental violin with thick plates were thinned, first the top plate and thereafter
the back plate. The following changes of the frequency responses were noted. There
STL-QPSR 4/1993
was a large change in the 500 Hz range for the top plate thinning and a moderate
change in the bridge hill range for the back plate thinning, see Fig. 3. The test player
found that the thinnings improved the tone. The top plate thinning gave a strong but
"colourless" tone, and the back plate thinning resulted in a strong, bright tone with
edge. The result indicates that the top plate mainly influences the tonal strength and a
subsequent adjustment of the back plate mainly influences the tonal brightness.
dB
THICK
PLATES
10.0
Log Hz
200
5k
50.0
dB
TOP PLATE
THINNED
10.0
Log Hz
200
I
I
I
I
I
I
I
l
5k
I
i
I
I
I
dB
AND
BACK PLATE
THINNED
10.0
200
Log
Hz
5k
Fig. 3. Frequency responses (level) of violin with thick plates, top plate thinned and back
plate thinned, respectively.
EXPERIMENTS ON SOUNDPOST ADJUSTMENTS
Sound post experiments were made with violins with prominent bridge hills. First, the
frequency response was measured for a violin with and without soundpost. It showed
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STL-QPSR 411993
an interesting difference in the 500 Hz range - the 450 Hz 'peak vanishes and the 550
Hz peak level increases much when the sound post is removed, but the bridge hill is
little effected, see Fig. 4. The effect of the removal reminds of moving the sound post
towards the centre line (cf. below) and the "locking" of the left f-hole edges, i.e. gives
a more symmetrical violin. The result indicates that the sound post should mainly
influence the low frequency response.
Secondly, the soundpost position was shifted towards and away from the bridge
(along the violin f a soundpost width). The bridge hill got a sharper and higher tip
with the sound post moved away from the bridge, see Fig. 5 . The player's judgement
was that the violin had a "slow and hard" tone with the soundpost close to the bridge,
and a "non-singing and loose" tone with the sound post away from the bridge.
Thirdly, the sound post position was shifted towards and away from the center line
(across the violin f a soundpost width). The sound post position gave a large influence
mainly on the 650 Hz resonance, see Fig. 6 . The 650 Hz peak level increased with the
sound post shifted towards the center line. In large, it may be concluded that the lowfrequency is suppressed by moving the soundpost towards the center line. The violin
was found to get a "looser" tone with the soundpost towards the centre, more rumbling
and harder tone with the soundpost away from the center line. The results of the
soundpost shifts indicated that sideways shift mainly influences the low frequency
response and the lengthways adjustments the high frequency response.
-10
I
I
1
1
1
1
dB
WITH
SOUNDPOST
-50.0
200
Log Hz
5k
WITHOUT
SOUNDPOST
Fig. 4. Frequency responses (level) of violin N92 with and without soundpost, respectively.
I
STL-QPSR 411993
- 1.0
I
dB
SOUNDPOST
TOWARDS
BRIDGE
f
@
-50.0
Log Hz
200
5k
-10
I
I
l
l
dB
SOUNDPOST
AWAY FROM
BRIDGE
-50.0
Fig 5. Frequency responses (level) of violin N92 with the soundpost shifed towards bridge
and away from bridge, respecively.
SOUNDPOST
TOWARDS
CENTER
SOUNDPOST
AWAY FROM
CENTER
Fig. 6. Freyae~zcyrerponses (level) of violin N92 with the soundpost shvted towards and
~ l c v a yfrom center line, respectively.
11
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STL-QPSR 411993
VIOLIN PROPERTIES AND TIME HISTORY OF VIOLIN TONES
The time history (an oscillogram) of a complete violin tone (open G-string played martellato) shows only a smoothly changing envelope, a portion enlarged 25 times shows a
time history reminding of a picket fence and with 150 times enlargement it shows time
histories of reverberation between the excitation pulses, see Fig. 7.
Fig. 7. Time history (oscillogramj of a violin tone stepwise enlarged: the complete violin tone
(open G-string played martellato), portion enlarged 25 times and 150 times, respectively.
STL-QPSR 411 993
ments have been noted. The results suggest in large that
1. the top plate and soundpost adjusted side-ways sets the low frequency response
and tonal strength,.
2. the back plate and the soundpost adjusted lengthways sets the high frequency
response and tonal brilliance.
It should be pointed out that the results were found by coarse adjustments and for a
limited number of instruments. Still we believe the results to be valid in general for
well made violins.
Additional experiments showed that
3. Effects of resonances can be traced as reverberating resonance tones between
the excitation pulses also in the airborne sound.
In informal listening tests with digitally produced impulses exciting digital filters it
was found that three resonances at 450 Hz, 530 Hz, and 690 Hz, and a resonance in the
bridge hill region, could clearly be heard - the Q-factor of a resonance gives double
influence (high initial amplitude and long reverberation). A drone timbre is clearly
heard for a fundamental frequency up to 500 Hz, but at higher frequencies the impulse
socnd will dominate, which indicates that the slip-stick transitions at the bow-string
contact has a dominating influence.
ACKNOWLEDGEMENTS
The project was supported by the Swedish Natural Science Research Council and the
Wenner-Gren Foundation for Scientific Research.
REFERENCES
Jansson, E., Niewczyk, B., and FrydCn, L. (1992). "Experiments on the construction and the
function of the violin", Catgut Acoust. Soc. J., Vol. 2, No. 2 (Series 11), November, pp. 6- 11.
Jansson, E.V. (1990). "Violin timbre and the picket fence". STL-QPSR 2-3/1990, pp. 89-95.
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