Bilbao Project Presentación

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Bilbao Project

Our intention as a group is to make a systematic study of a group of violins, for which we have a great deal of structural information and acoustic measurements, culminating in a psychoacoustic evaluation event (a playing and listening test). The kind of answers we are looking for are both visceral and intellectual. We need the hands-on connection with the parts during making; the sound and the playing feel; and these sensory experiences reinforced and extended through the complementary lens of detailed modal analysis and sound radiation measurements. We have one foot in the realm of aesthetics, imagination, intuition and manual skills, and the other where our decisions are informed by a systematically organised body of knowledge relating to the perception of sound, material properties and structural vibration. This is a very exciting place to be, not something to fear.

The big breakthrough at the beginning of this project was the decision by the Basque violin making school in Bilbao (BELE, see page 50) to work with us, both by engaging their students in making instruments for the project and in obtaining funding from the Erasmus+ EU education programme for travel and other costs. So it was that in September 2016 we were able to start meeting as a group and thrashing out the details of the experiment’s design. The team includes maker and philosopher Roberto Jardón Rico, BELE acoustics teacher Unai Igartua, maker and restorer Andrea Ortona, and Paris-based psychoacoustics researcher Claudia Fritz. Professor Jim Woodhouse of Cambridge University agreed to support us in an advisory role.

Background

An ancestor of our experiment took place in Stockholm in 1984, devised by Jesús Alonso Moral, then a PhD student working with Erik Jansson at the KTH Royal Institute of Technology. Three tops, three backs and three rib garlands were selected from a pool of ten, five and five respectively. Each plate was characterised as ‘pliant’, ‘normal’ or ‘resistant’ on the basis of mode 2 and 5 frequencies, and the ribs by thickness. ‘Normal’ was close to the average frequencies of the whole set; pliant was in the low range; and resistant in the high range. The possible combinations of tops, backs and rib garlands was 27 violins, of which 12 were built in that experiment, but only a few could exist simultaneously. More detailed measurements were recorded for the plates, although they were not matched for density or elastic modulus, and the archings were deliberately different. All the plates were supplied by Hutchins and bi-octave tuned, which makes sense in the historical context. The objective of this experiment was to determine how the mode frequencies of free plates affected the modes of the violin when assembled. Moral further sought any correlation between player preferences and mode frequencies of the completed instruments.

In 2012, team member Andrea Ortona organised a revised version of Moral’s experiment at the international violin making school in Cremona. Moral had found that the ribs were the least significant factor, and Ortona opted to keep to standard, medium ribs, allowing him to concentrate on the plates. Therefore there were only nine combinations of the three types of plates. The experiment was run twice, with a total of 18 instruments built. All the violins were from the same model and arching templates. For administrative reasons, Ortona was not able to have as much control over the selection of wood as he wanted. The plates were characterised as ‘thin’, ‘medium’ or ‘thick’ but the main criterion was mode 5 frequency. This strategy partly compensated for the variations in density but tended to pull the plate impedances towards a similar value. At evaluation, two stood out as preferred while the others were so similar that it was difficult to discriminate between them. The purpose was to provide a hands-onexperience for the students in which they could observe the effect on thefinished instruments of combining these different plates.

Project Description

Six instruments will be built at BELE and preserved as a resource for subsequent generations and visitors to the school. There will be three instruments with normal backs, each paired with a pliant, normal, or resistant top. Similarly, there will be three with normal tops, each paired with a pliant, normal, or resistant back. There will therefore be two examples of normal top paired with normal back, serving as a control. We have wood for tops and backs that is closely matched in density and sound speeds – all tops and backs from the same trees. Since the wood is well matched, both the weight and frequencies – and therefore also the impedance estimate – will be strongly correlated to the thickness. We have decided to go for greater control by having all plates and scrolls cut by CNC routers. The outside surface will not be changed during the experiment, with the graduation performed entirely on the inside surface. Thus our plates will have closely matched characteristics apart from the single parameter of thickness, and it will therefore be more likely that it is this structural feature that is responsible for the perceived playing difference.

The collection of violins to be evaluated will be expanded by several extra examples built by professional makers from diverse countries and backgrounds. They will provide their own wood, which must be within a specified density range, and they will retain ownership of their work. The parts will also be cut by CNC. While the school instruments will be built to very strict specifications, the external makers are free to decide how to make the best use of the wood that they have selected. However, we are asking them to document their work in some detail.

Sam Zygmuntowicz and Joshua Bell have kindly allowed us access to the CT data for the ‘Huberman’ Stradivari to use as the model for our violins. Although we could have concocted a perfectly viable model to replicate, we felt that using a prestigious original would add excitement to the project, plus a couple of extra learning dimensions. Actually working on a close replica of an original plate or scroll is an encounter that might lead to a better internalisation of the shape than is provided by the more usual routine of working from templates. Students will also learn something about CT and the potentially contentious CAD wizardry employed in generating the files that control the CNC router. For some this heralds the death of violin making as we know it, but obviously these technologies are here to stay and we believe it prudent to understand them and make informed choices about their use.

Since BELE is in the same building as the Conservatorio Profesional de Música Juan Crisóstomo Arriaga, we have access to an excellent recital room and concert hall for our evaluation work. Previous experience with playing and listening tests show that those who only listen are less consistent than players. Players have much more information on which to base their judgements, and are more self-consistent, but they do not always agree with each other or the listeners. Among other evaluation methods, we plan to use sorting by free categorisation: musicians will be asked to group the violins according to how similar or different they are, using as many or few groups as they feel are needed. When this method has been used in previous experiments, different musicians made similar groupings, though offering different explanations for their decisions. Up to a point, we can slip through the linguistic minefield: individuals attach different meanings to the same word and it can be difficult to tell exactly what they intend. We will consider directly how the configurations of plate characteristics (as embodied in a particular violin) are ranked and how far such configurations can be characterised by verbal description or acoustic measurements. We hope this will enable us and other makers to identify where our instrument lies in terms of these characteristics and therefore how we could move in a desired direction.

The evaluation phase will take place next year. The plans are still a work in progress but we envisage a public event where people who are interested can hear the violins, examine and play them. Several detailed publications will also be produced.

 

Members of the Bilbao Project

Claudia Fritz

Jim Woodhouse

George Stoppani 

Andrea Ortona

Roberto Jardón

Unai Igartua

Sponsors

alava-group-verticalAlava Ingenieros

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