thedivide‘What has struck me most about

the craft over the past 30 years isthe growth in openness amongmakers, the decline in secrecy,’remarks Woodhouse. ‘Though thereare still makers who are scepticalabout science – and quite rightly so – there is now a critical massof people who are interestedin exchanging ideas and thatis moving everything forward.’

Woodhouse was brought upin the suburbs of Brighton, onthe south coast of England, wherehe showed an early aptitude formathematics along with an enthusi-asm for making things. At 14,in the thrall of Jimi Hendrix,he built an electric guitar. ‘I grew upin a do-it-yourself household,’he says. ‘There was always a workshop around.’ As an under-graduate at Cambridge he believedhe would become an astrophysicist,but his life changed direction whenhe took Juliet Barker’s long-runningevening class in instrument making.He built a classical guitar, thena violin and he has since completedtwo string quartets. Woodhouse’sfascination with instrument makingled him to a doctoral thesis in violinacoustics under the supervisionof atmospheric physicistMichael McIntyre. ‘Michael is alsoa really fine violinist,’ Woodhouseexplains. ‘I was told that as a youngman he entered a major competition,promising himself that if he wonhe would give up science andbecome a full-time violinist.Well, he came second.’

While some researchers havedevised and promoted ‘scientificallybased’ systems for building instru-ments, Woodhouse carefully avoidsthat sort of thing. ‘It’s no usecoming in and telling makers whatto do,’ he says. ‘Scientific adviceshould come with a governmenthealth warning, “May be harmfulto your instrument!” Science can beuseful in sending you in the rightdirection, but if you follow sometheory to the point where you startto think, “I don’t want to do thisbut science says I must,” thenthe science is probably wrong.’He offers this advice: ‘Don’t makeyour violin unusually thick or thin

At the stately William Penn Hotel

in the once sooty, now cleanlyscrubbed city of Pittsburgh,Pennsylvania, members of theAmerican Federation of Violin andBow Makers (AFVBM) gather forthe 2005 convention – three days of lectures, exhibitions, panel discussions and banquets.A distinctly British voice among the generally North American mix belongs to Jim Woodhouse, a Cambridge engineer and one ofthe most highly respected figuresin violin acoustics. He has beenflown in to talk about his recentwork on the violin bridge. In itspublished form, the work is highlytechnical, but Woodhouse has the

rare ability to explain complex ideasin cheerful, workshop English. Healso has a genuine interest in theway that violin makers approachtheir work.

‘I like to tag along behind them,’says Woodhouse, ‘and listen tothe kinds of things they talk about.It’s one reason that I follow TOBI[a web-based forum on bowedinstrument technology].When violin makers ask questionslike, ‘What will happen if I cut a bitmore wood off the f-holes here?’there’s no way science can answer,at least not yet. We’re still gropingfor the right way to frame thesekinds of questions. But everyso often something comes alongthat I think I can say somethinguseful about.

‘There is also an educationalprocess I can help with. Makershave mental models of vibrationand sound – it’s part of theirintuition. These models may workwell enough in practice, though notalways for the reasons the makersthink they do, but sometimesthe model is quite obviouslyupside down and that’s whereI can have a role in cutting outsome of the rubbish.’

The day before his talk,Woodhouse and I find a tablein a quiet corner of the richlyornamented hotel lobby.Loudspeakers hidden high amongthe marble arches have been playingthe same violin recording forthe past two days – perhapsin honour of the convention.Makers with nametags wander inand out of an adjoining Starbucks.

44 The Strad August 2005

Bridging

ABOVE Woodhouse inhis Cambridge office

Joseph Curtin speaks to violin maker and engineerJim Woodhouse about communicating acousticsresearch to today’s making community

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or bizarre in some way, just toachieve an octave relationshipor some other such thing.Good violin makers make goodviolins. Science follows alongbehind. There’s no way scientistsare going to tell makers how, in anygeneral sense, to do their job better.’

Woodhouse believes, however,that there are ways in which sciencecan help. ‘The wolf note is anunusual example of how a perfectlystandard bit of engineering can beused to solve an instrument-makingproblem,’ he explains. ‘Woodselection is another area thatwe know more or less how toapproach. Old violins don’t lendthemselves to being cut into teststrips, so we have to get at the woodproperties indirectly. The experimentyou want to do is measure a pieceof wood thoroughly, wait 300 yearsand then measure it again. It wouldbe very nice to find Strad’s woodstore. How does 400 years of airdrying and humidity cyclingchange a piece of spruce? Old woodgets chalky, doesn’t it? It crumbleseasily. My best guess as to how itdiffers acoustically from new woodis that the high-frequency dampingis greater. This might explain whyold violins seem better at suppress-ing the high-frequency noise thatcan make new ones sound harsh.’

How far has science come inunderstanding the violin?Woodhouse uses the image of ajigsaw puzzle. ‘The edges are done,along with a few bits in the middle,’he says, ‘but much of the pictureis still blank. A jigsaw puzzle isa good image for how sciencegenerally proceeds. We do theedges first because they’re easier,then we work our way in.The strong point of science is thatit is cumulative. I am completelyconfident that more and more ofthe picture will appear. It will takegenerations more learning and wemay never know everything thereis to know about the violin, but it’sthe attitude that is important.’

One name which often comesup in the conversation is thatof Woodhouse’s late friendDavid Rubio: ‘He had the mostcolourful background of any violin

maker I’ve met and he’s the onlyperson I know who actually ranaway from home to join the Gypsies.’Rubio became a flamenco guitaristand then a renowned classicalguitar maker before turning hisattention to the violin. In the mid-80s,Rubio approached Woodhouse andasked if he thought there wasanything to John Chipura’s ideasabout mineral grounds (The Strad,July 1984). He also approached twoother Cambridge scientists,the chemist Ralph Raphael andthe materials scientist Claire Barlow.A research collaboration was born.In 1989 Barlow and Woodhousepublished a two-part Strad article(March and April) that lent newcredibility to the concept of mineralgrounds – causing a spike in thesales of pumice, volcanic ash, micaand other such particulates.

Rubio and Woodhouse went onto work together on a number ofresearch projects. For one of them,Rubio built a set of six violins.Each has carefully calibratedinternal differences, but theiroutward similarity makes itdifficult for players to tell themapart by visual clues or by feel.Woodhouse has a photo of theinstruments, laid out front-to-backon a straw mat, as a screensaveron his laptop. After Rubio’s deathfrom cancer in 2000, his toolsand forms passed to Woodhouse’s

guitar making son, Martin, whomRubio had taught.

Woodhouse’s talk is scheduledfor 8.30 on the final morning ofthe conference. When speaking,he tends to sway from side to sidewith enthusiasm and his deliveryis as informal as his dress. He refersto a complicated looking graphas a ‘wiggly line’ and explains whyviolin makers might want to takea second look at it. ‘Violins may allbe different,’ he says, ‘but they’reactually no more different, one fromanother, than most other manufac-tured objects.’ He then showsa slide of the sound output of tenold Italian violins – ten wigglylines laid on top of each otherto show a range of individualdifferences and a commonoverall shape. ▲

45The Strad August 2005

‘A JIGSAW IS A GOOD IMAGE FOR HOW SCIENCEGENERALLY PROCEEDS. WE DO THE EDGES FIRSTBECAUSE THEY’RE EASIER, THEN WORK OUR WAY IN’

Figure 1 The vibration mode of a violin bridgeassociated with the ‘bridge hill’

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A wave of laughter ripples acrossthe room as the audience digests thenext slide, which shows roughlythe same range of differences inthe acoustical behaviour of 98 carsoff the same production line andthen of 41 nominally identical beercans. ‘The thing about violins is thatpeople care about the differences,’Woodhouse says. ‘With most noiseand vibration problems, the clientisn’t much interested in the finedetails of the acoustical behaviour;they just want to know where to slapa little damping to make the noisego away. The violin is almost uniquein that the fine details matter – toan almost ridiculous level – makingit a good challenge for the scientist.’

An acoustical feature that fineviolins seem to share, Woodhouseexplains, is a broad peak in soundoutput between about 2,000Hz and4,000Hz, around the regionof the ear’s greatest sensitivity.Swedish researcher Erik Janssoncalled this peak the ‘bridge hill’,on the assumption that it was createdby a resonance of the bridge itself(see figure 1). Jansson showed thatby tuning the frequency of thisresonance, the violin maker can tosome extent control the instrument’streble response and thus its brillianceand projection. Further researchindicated that the characteristicsof the bridge hill are determinednot just by the frequency of thebridge resonance but also bythe mass of the bridge, the distancebetween its feet and the ‘springiness’of the top upon which it sits.

Woodhouse has applied someof the latest tools from vibrationtheory to create a mathematicalmodel of the bridge on a violin,in an attempt to determine thecontribution of each of theseparameters. This model exists onlyon a computer, but when the instru-ment was set into virtual vibration,a bridge hill did indeed appearin its response curve. Woodhousethen independently varied eachparameter, plotting graphs toshow how each change affectedthe bridge hill (see figures 2–6).

Never one to sail away on a theoretical model, Woodhouseasked Cambridge violin maker ▲

47The Strad August 2005

Figure 4 The skeleton curve of the bridge hill as the bridge mass is increased – by adding

a mute, for example. The dashed line represents the lightest bridge

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Figure 2 the frequency response of a simplified violin, as modelled on a computer.

The skeleton curve (dashed line) shows the bump of the bridge hill

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Figure 3 The skeleton curve of the bridge hill as the bridge thickness is reduced.

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Jonathan Woolston to fit threedistinctly different bridges on toone of the Rubio violins, whichwas then given to players forevaluation. This preliminaryexperiment nicely confirmedhis predictions. He has broughtthe three bridges with him toPittsburgh and holds them upfor the audience, explaining thatthey are DeJacques models withadjustable feet, so makers with aninterest are welcome to try themon their violins.

Every maker knows that tinyvariations in the cut and design ofa bridge can make large differencesto the sound of an instrument –differences that can make or breaka sale. Woodhouse’s results providea kind of map for violin makerswishing to systematise theirapproach to bridge cutting. If hispredictions bear out, makers havea surprisingly large and perhaps

under-exploited degree of controlover one of the violin’s most crucialacoustical features, the bridge hill.This is some of the best news to comeout of the research communityin years.

The AFBVM meeting finishes thatevening with a banquet. Organisersand guest speakers are publiclytoasted and warmly applauded.As the waiters clear away the lastcoffee cups and wine glasses,an end-of-convention nostalgia fillsthe room. Woodhouse tells meabout his next violin project –a virtual instrument to be builtwith digital filter technology.Tonal changes that might take weeksto implement on a real violin willbe achieved in a few keystrokes.The instrument will be played byrecorded string signals from realplayers and heard via loudspeakers.Panels of listeners will fill outquestionnaires for later analysis.If all goes well, another piece willfall into place on the jigsaw puzzle. S

48 The Strad August 2005

RIGHT the six violinsmade by David Rubiofor a joint project withWoodhouse. They havecarefully calibratedinternal differences, butare outwardly identical

THE RESULTS PROVIDE A MAP FOR MAKERSWISHING TO IMPROVETHEIR BRIDGE-CUTTING

Figure 5 the skeleton curve of the bridge hill changing as the distance between the bridge feet

is varied. The dashed curve has a spacing of 5mm, then 10mm, 20mm, 30mm and 40mm

Figure 6 the skeleton curve of the bridge hill as the top plate is thinned near the bridge.

The dashed line represents the thinnest plate

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