This article was first published in The Strad November 2008

 

I could see a trend developing even before the seven-day VSA Oberlin Acoustics workshop started. More and more violin makers who attend the preceding violin makingworkshop are staying on for a third week in this small Ohio college town in order to improve their acoustic understanding, exchange ideas and learn new skills. When in past years there might have been an overlap of just two people between the two workshops, this year five of the 40-or-so participants in the violin making workshop went over to the ‘dark side’ of acoustics. This is in good part because violin acoustics have moved from purely theoretical heights to a practical level: violin makers are now using their advanced acoustic understanding in their day-to-day workshop practice.

Saturday 28 June

Organisers and participants start arriving in Oberlin and over a dinner-time burger in The Feve, one of our favourite eateries, those of us extending our stay in town witness one familiar face after another come in. People have travelled from all over the US and Europe, and even from as far as Japan. My particular aim this week is to understand more about modal analysis. This is a technique that measures how the different parts of a violin vibrate when it is played – the idea being that by identifying the movement characteristics of great instruments, one can more closely copy them. One of the people doing the most interesting work in this field is George Stoppani, a violin maker based in Manchester, UK, and a tutor for this course. George and I spend the evening planning the project we will be pursuing with American maker Terry Borman this week: to try to turn a cheap factory fiddle into a ‘Stradivari’ using the results from modal analysis.

Sunday 29 June

After a late breakfast in a local café, I prepare to put thoughts of practical violin making aside for now, and let acoustics theory kick in. The workshop starts at 11am with introductory lectures, a comfort to the slightly nervous and intimidatedlooking violin makers. The workshop’s organiser and co-director, Fan Tao from D’Addario, introduces acoustic terms, and Evan Davis of Boeing explains the impact hammer rig (a measuring set-up) andfrequency response, and talks about body modes.

At 2pm Professor Colin Gough, from Birmingham University in the UK, goes over sine waves, partials and sawtooth waves, and sparks off fantasies about palm trees and beaches when he talks about ‘the island’ and its importance. Unfortunately he’s referring to the space between the f-holes – another dream gone. Joseph Curtin, violin maker and workshop co-director, rounds off the afternoon with a talk on weights and tap-tones in old Italian violin tops. After dinner I have a conversation with fellow luthiers James Ham and Ted White about the benefits of fingerboards that are extra light and extra stiff. It’s fascinating stuff, and we resolve to find time later in the week to take it further with input from other interested participants. Then it’s back to our meeting room in the Oberlin Conservatory of Music for an evening of introductions to the other participants. There are around 40 of us in all, and it’s certainly an interesting and diverse mix. It starts off on the heavy end with physics professors, retired researchers of superconductors, modal analysis experts from the aircraft industry, and so on. Then there are musicians and violin makers, some of whom have already dedicated many years to acoustic research, while others have only recently developed an interest and have more basic questions. But we all share an enthusiasm for the complex riddle that is stringed instrument sound.

Monday 30 June

The day starts with a session of lectures. I find a bench space within view of the lecturers since I want to finish the morning not only with some more knowledge in my head but also with a fully set-up violin – the one to be transformed. Joseph Curtin gets everybody’s attention by slowing down sounds, including birdsong that turns into a melody that Ravel or Debussy could have written. He also slows virtuoso violin music, transforming it into something resembling the sound of a double bass, which makes every little slide and inaccuracy obvious. Then he plays a passage of music, recorded on an electric violin, on to which he adds a series of sound radiation profiles – a kind of acoustic thumbprint taken from specific Cremonese violins using the impact hammer rig. The track thus ends up sounding in turn like the ‘Plowden’ Guarneri ‘del Gesù’ and the ‘Wilmotte’ and ‘Titian’ Stradivaris. It’s a good way to hear the different sound characteristics of these instruments without the variability or the compensation of a player being a factor. During the lunch break the strings go on to the factory fiddle. It’s a bad instrument and whatever we do will improve it. In the afternoon we are presented with the various projects that will fill our afternoons and evenings. The projects are split between about a dozen groups of participants: there is a group discussing the impact hammer rig; a group working on acoustic differences of cello bridges; an ‘island’ research project; our planned transformation through modal analysis; and many more.

In the evening we start to assess formally our factory fiddle’s playing qualities – or lack thereof. Expert violinist Nori Tagawa plays it for us, but even after we make some considerable improvements by adjusting the soundpost, the violin still sounds very shallow and boring. We then make our first modal analysis of the front, and the results confirm that it’s a dreadful instrument.

Tuesday 1 July

George Stoppani starts the day with a stimulating talk in which he shows animations of several Stradivaris through all the frequency bands. The great thing about this is that you don’t need to understand how modal analysis works: anybody can understand the moving images. Seeing, for instance, how an f-hole wing moves will make you pay more attention to its design. In the early afternoon we have a demonstration of several innovative violins. I’m particularly intrigued by Douglas Martin’s balsa violins. He works with unconventional designs and the extra-light but stiff wood enables him to make powerful-sounding instruments. After several years of work, he’s managed to make them sound very close in tone colour to conventional violins. Later we continue the analysis of our bad violin and look at some animations of it. It really does have some serious issues – its modes have nodal lines going unusual ways – and we will need to do some serious rethicknessing. We also wonder about the bass bar and if we will need to replace it.

Wednesday 2 July

Joseph Regh in his presentation pinpoints an interesting research direction by introducing vibrations of a particular frequency into a bow at the frog end which hinder the slip-stick action that is required to get the string vibrating. Maybe the ability to go through the whole frequency spectrum might give us more insight into what makes a bow work. The session that gets everybody talking is Terry Borman’s presentation on using CAT (computed axial tomography) scans to take detailed measurements of wood density in old Cremonese and modern instruments. He has found a smaller density difference between late and early growth in the Cremonese violins compared with the modern instruments. This gets everyone speculating about plausible explanations and consequences. After lunch, George, Terry and I meet to discuss what to do with our violin. We decide to take the plates off to rethickness them, since we need to remove more wood than we are comfortable to do from the outside, and we also want to compare the free plate resonances with he modal analysis results. We take the iolin apart in the workshop space of the Advanced Topics violin workshop (which runs during the same week as Acoustics), where Christopher Reuning has brought some nice fiddles to show. They include an Antonio and an Omobono Stradivari, a very nice Giuseppe ‘filius Andrea’ Guarneri and a Giovanni Battista Rogeri. We grasp the opportunity and ask if we can do modal analysis measurements on two of the instruments. Chris agrees immediately and we arrange to get the violins after dinner. We’re in for a long evening. After picking up the violins, George and I get going. We are going to measure one violin each, the Antonio Stradivari and the ‘filius Andrea’. Unfortunately we both start off with computer problems that cost us lots of nervous energy, and time begins to run out. Finally both systems are operating and with one assistant each we race through the measurement points. We finish just before midnight and can return the instruments. I need a beer to calm down and get rid of the adrenaline still pumping through my veins.

Thursday 3 July

Over breakfast we find ourselves discussing new versus old violins and their respective merits – not an undisputed subject. At 9am George Bissinger, professor at East Carolina University, delivers an attention-grabbing talk with practical consequences. He shows how the placement of the two B1 modes can influence the output of the A0 (or Helmholtz) mode. This is very important for the lower register of instruments.

 

Colin Gough might have had a difficult slot after that, but his advances in finite element analysis keep everybody interested. This is a system that essentially allows you to build a computer-model ‘virtual’ violin by defining parameters – shape, density, stiffness, damping, and so on – which can then be changed to see the effect By being able to change one parameter at will and observing the outcome we can learn a lot about the way our instruments work. The more accurate this model becomes, and the closer it is to the real thing, the more useful it will be to us as makers. In the afternoon we finish rethicknessing both of our bad violin plates. We feel that we don’t need to replace the bass bar but will reshape it instead. We glue the back on to the ribs before dinner, and the front after eating. then get a short private tutorial onhow to produce the fantastically revealing moving images in George’s software – I hope I can remember all the steps. As we finish, Fan Tao asks me to join him, Colin Gough and Brian Newnam to play a string quartet, so we read through the Mendelssohn E minor. Then George, Terry and I string up our ‘bad violin’ – the glue has had enough time to dry – and rename it the ‘not so bad violin’.

 

The difference is remarkable, and so far we have pretty much only done what any capable violin maker would have done, although backed up by our modal analysis. The strength of the technique should really show in the next step, when things are not nearly as obvious any more. But it’s too late to carry out any more modal analysis and we retire with other course members for whisky and prawns.

Friday 4 July

At breakfast I greet the Americans on Independence Day with a toast to the royal family – I just can’t resist – but no nationalistic heckles rise, so we turn to talking about acoustics again. This morning, George Stoppani’s moving images again grab our attention. But this time he shows us not the actual movement of the plate but where and how the plates bend most: longitudinal, transversal and twisting. In the case of the front he is also able to show us with colours where the bending energy is stored. This will give very good indications as to how to change modal behaviour deliberately. It’s all very exciting: I’m really looking forward to working more on this for myself. Late in the afternoon I try to measure our ‘not so bad violin’, but my computer and measurement equipment play tricks on me. Just before dinner time the technology cooperates again and I decide to try an extremely quick non-averaged modal analysis of the top plate. After dinner George and I analyse the violin properly and have a quick look at the results. They seem to fit with what we heard, which is again reassuring. We go some way to identifying the path of future proceedings but sadly, we’re out of time to do the next step this week. It’s something I’ll be continuing back in my workshop in London. It’s high time to pack away nearly 50kg of tools and equipment, all of which needs to find space in my suitcases. Well after midnight, we find the participants of the Advanced Topics violin workshop having fun on the terrace of their residence. Time for the last beer of this year’s Oberlin.

Saturday 5 July

The morning consists of the presentations of results of our various projects. I also give a short presentation on a little research project that Hans Pluhar and I carried out in the two previous weeks about correlation of plate stiffness, weight and free-plate frequencies. Over lunch the whole workshop is scrutinised and shortly afterwards I take my shuttle to the airport. It’s time to enter the real world again, but I will continue the acoustical work and am looking forward to more inspiring input at the next acoustics workshop in 2009.