Towards targeted design
Acoustic guitars have been built for over 200 years in the current form. Antonio de Torres is considered as the father of the modern acoustic guitar and his design is still the prototype today for classical guitars. That is an amazing fact since it is atypical for innovation of products. Apparently there are forces in play, both at the sides of the makers and the players, which cause this time path. One such force is the limited understanding of what in the guitar brings that specific tone about. The builder may rely on the lore of guitar building, which is based on traditional design. In this way one would not go astray and end up in unknown terrain. While digging deeper into this phenomenon, it became clear that the ideas expressed on the internet on how an acoustic guitar actually works and can be designed to produce a certain sound follow a pattern. Facts and beliefs are often massaged to philosophies which only hold up against superficial consideration, but not to scrutiny. This belief in a personal truth is only human, trying to comprehend the many observed phenomena. Those interested may read about the Dunning-Kruger effect, describing in 1999 the illusionary assessment of own cognitive ability by those with little knowledge as greater than it is and the underestimation of experts of their cognitive ability (https://en.wikipedia.org/wiki/Dunning-Kruger_effect). This effect has been assessed in several fields of knowledge. Crowe and Youga (1986) had already assessed that experts learn more than novices from additional information, despite the simple fact that novices have more to learn. Both studies show that information goes through a mental sieve and the finer the mesh is, the more is recognized, retained and incorporated in the mental framework. This refines the sieve and the finer the sieve is, the stronger the belief is that there is even more out there, because the more one knows, the more of the information raining down is recognized. This is easily noticed in the modesty and reservations expressed by expert luthiers in discussions. Recognition of attitudes helps to sort information sources. The purified facts from these sources are impressive and come from musical science, human factors, physics and engineering. And it comes from a great deal of experience of luthiers and musicians.
What is holding back the full use of knowledge is the difficulty partners in the development chain have to comprehend the full scope of complexities. This happens more often with products involving engineering, styling and crafts. In the clothing branch, for instance, the chemical corporations producing fibres and treating textiles have the deepest knowledge of materials, but their gateway to the market is through the designers and marketers of clothing. This knowledge gap has closed over time. The craftsmen who used to make the clothing have become factories, which take production orders, based on engineering specs provided by design and marketing corporations. The latter are the names we know from the shopping centers. They have become the leaders of the chain.
Production and marketing are in guitar land unified in factories which do series production. The crafts are reserved for exquisite guitars, made in unique copies by master luthiers. Only few of the factory staff and luthiers have deep understanding of the physics of the guitar and can handle the math involved. Apparently, in crafts design follows another route, based on experience, starting from a successful design. This may have led to the use of plans, ways to produce good instruments if you stick with it. Is there no drive for innovation from the part of the players? This may be a deadlock called tradition: if something new is not appreciated it will not be offered and something not offered will not enable appreciation. This is certainly the case in the classical department. But also in the more marketing driven steel string department the innovation is more facial than bodily. The financial consequences of ‘educating the customer’ are prohibitive for radical experiments. Why is clothing then so more various than guitars? Well, for one reason clothing is less bound to technical restrictions. And its lifetime is so much shorter that fashion is more likely to drive the purchase. If we were used to buy a new guitar every season the industry would rapidly adopt variation in build and looks. Certainly so if there was a marketing force called high fashion. Sitting a while on this problem helped to recognize that the cost of experimentation needs to fall and key to that is replacement of trial and error by targeted design. Imagine that one could set an acoustical target, enter some design choices and materials in a black box and out comes the design that does exactly that. Is this a phantasm? Not in the clothing industry. Instead of producing clothing, showing it in a shop and waiting if sufficient customers are willing to buy, clothing companies now start asking customers what they want and then produce unique copies of custom style and fit clothing in a matter of days. Was that not what a tailor used to do? Yes, but not in mass production. Much of the success depends on the capability of the corporations to adopt this so called chain inversion and to cope with the new challenges involved. Important, however, is that the enabler, a knowledge driven design process, is feasible and in place. Once again, is this a phantasm for guitar design or a realistic option? This book demonstrates that the current state of knowledge is promising to support such a process. Moreover, it may help innovators to make modifications which are desirable for good reasons, but beyond the comfort zone of many luthiers.
The use of simulation
In this part of the book it is tried to create a consistent view on the many acoustic issues of the guitar. This is the place where practice and theory merge. Much of the theory is put in simulation models, which are calibrated against measured data. Many readers will have their reservations with simulation. How close is that to reality? Is it useful anyway or a toy? Is a simulation not more laborious than a trial build? These are fair questions and in science they are summarized in the concept of ‘Fit for purpose’. Not the reality level is the issue, but under which conditions the outcomes are reliable. That is why calibration is so important. On the other hand, see the advantages. With simulation it is possible to integrate knowledge from such diverse sources as physical laws validated elsewhere, measured parameter values, materials, engineering, data regression, logic or psycho-acoustic perception. The model helps to train the user in understanding the complexity and merciless uncovers false reasoning. An alternative way would be to build guitars and measure their properties. Also this involves validity issues, because there would be no clue for uncovering the causal relations behind the measurements. How could measurements be converted to predictive power if there is no deeper understanding? Decisive, however, is the practical side. In the studies done here many hundreds of precisely defined simulated guitars are studied. Producing these in the material world would take a luthier’s lifetime of work, compressed in time. This whole issue is well illustrated by luthier Paul Jacobsen in his essay ‘Tone variables in guitar construction’ (https://www.pjguitar.com/articles/tone-variables-in-guitar-construction/). Being a luthier, he made serious attempts to approach guitar building as a scientist. Despite his greatly appreciated efforts his experiments demonstrate how both difficult and tedious this is. Experimental design is a serious psychological branch and he made some omissions and errors (no reproduction, no investigation of interactions of variables, no assessment of error margin and validity range of the conclusions, no double blind listening, trying to prove an equality, serving as a subject himself) the avoidance of which would demand multiple times the labour he already invested. The cost and effort are prohibitive and the simulation alternative is affordable and relatively fast. It takes one or a few capable persons, spending a couple of years on collecting, processing and verifying the available knowledge and the forging of this information into realistic theories on which the simulations are based. Simulation has also limitations, notably the absence of the perception of tone. What simulation can do and has been practiced is generating synthetic tones which are then presented through headphones.
Chapter 7 shows the barriers involved in the generation of a voice. Expansion of the current knowledge to increasing reliability and versatility is desirable. Your input, reader, guitar builder, musician, tool maker, engineer, materials specialist is thus a valuable complement. The forum page of this site is your platform for feedback, identification of issues or contradictions and suggestions for improvements.