The Craft of Guitar Lutherie – Strength in Numbers


The Next Two Wood Ring Classical Guitars to be Completed Before the End of 2011.

Aaron and I have been working very hard to finish two beautiful classical guitars that he has been building, side by side.  One has a  Western Red Cedar top with Cocobolo sides and back.  It has Bocote trim and a Spanish Cedar neck.  The other guitar has a German Spruce top with Indian Rosewood sides and back. It has Bloodwood trim and a Spanish Cedar neck. We have been working on these two guitars for over two months now.

Although much of this time was spent in crafting the two instruments from their component pieces of wood, a significant amount of time was spent performing extensive tests at every level of construction. Our goal in doing such thorough testing is to have a very thorough scientific understanding of every step in the process of building each classical guitar we produce.

 Although this testing and record keeping takes a lot of time and work, we believe it is well worth it for three reasons.


  1. We want to be absolutely sure that each Wood Ring Guitar is built to last a lifetime. This is done by applying both theoretical and empirical data to our building approach in order to make sure that the most vulnerable parts of the guitar are strong enough to endure decades of playing (strength testing).
  2. We want to be able to reliably reproduce the qualities that contribute to a great sounding guitar (acoustic testing).
  3. We want to continually improve the building process and the finished product from both an acoustic and artistic point of view (record keeping, feedback, and analysis).

Our aim is lofty but we feel strongly about it.  We are committed to creating instruments that will gain in value over time because of their unique artistic beauty, their outstanding sound qualities, and a look and feel that gives each owner that special feeling that only a select few instruments throughout the world can bestow upon them.

Today, I want to discuss the process we use to test the strength of our soundboards. This testing process is very important because:

  1. It allows us to fine tune the soundboard such that we are absolutely sure that each guitar is strong and built to last.
  2. It gives us feedback in fine tuning the top and bracing system such that we can obtain the optimum sound characteristics possible.
  3. It backs up our commitment that the guitar will sound as good or better 10, 20 or 30 years in the future as it does the day it is purchased.

 Sound Board Strength Testing

It is the soundboard that is responsible for most of the sound that eminates from a guitar. When the player plucks or strums the strings, they start vibrating. This vibration is transferred through the bridge and into the soundboard. For standard guitar tuning, frequencies from 82.407 Hz (Open 6th string – E2) to 880 Hz (17th fret on 1st string – A5) are generated. To achieve this, a lot of tension (both static and dynamic) is exerted by the strings onto the bridge and the soundboard. The tension exerted by each string depends on several variables including (a) active string length, (b) frequency of the string, and (c) mass per unit length of the string. For a classical guitar the total tension exerted by all six strings is approximately 85 – 95 lbs. of force.  Due to the way the strings are attached to the bridge, the force of this string tension applies a rotational torque on the bridge and soundboard with the front of the bridge pushing down on the area between the bridge and the soundhole and pulling up on the area between the bridge and the bottom edge of the guitar.

Torque Exerted by Strings on Bridge and Soundboard

As a general rule of thumb, the less mass there is in the soundboard and bracing, the louder and more responsive the instrument will be. Of course there is a limit to this and in reality a luthier must find a balance between the soundboard strength and the amount of mass that the soundboard will have. As mass is removed from the thickness of the soundboard plate and the thickness and height of the braces, the more the soundboard will deflect and warp in response to the tension placed on the bridge by the strings. This is good to a point and every classical and acoustic guitar top deflects a small amount downward between the bridge and soundhole and upward between the bridge and bottom of the guitar. As long as this deflection is kept within some well established design parameter guidelines this results in great sound and a very durable instrument. If this deflection exceeds these guidelines, then over time, the top will start to deform and cracks may appear around the bridge. Ultimately the soundboard may collapse. This effect can be magnified if the guitar is exposed to extreme conditions of varying temperature and humidity.

 Testing Apparatus and Procedure

As part of our testing process, we use a method of soundboard stiffness testing and deflection compliance that was first suggested by David Hurd in his book Left-Brain Lutherie – Using Physics and Engineering Concepts for Building Guitar Family Instruments. This is an outstanding book on the application of science and engineering to the craft of Lutherie. In this book, David proposes that deflection measurements of the soundboard be taken at the point in the building process where the soundboard has just been attached to the sides and the back has not been attached yet. This allows the lutheir to make both soundboard thickness adjustments and bracing height and thickness adjustments based on results of the deflection tests and Chladni pattern tests.  

The apparatus that we use for deflection measurement was hand made and is based on David’s Luthiers Forum series of articles which outline how to build the apparatus and how to use it. The apparatus is simple and is cheap to build.  It is a well thought out apparatus for measuring guitar top deflections. After we built it and calibrated it, we performed extensive testing to establish repeatability and error values and we found that it can reliably measure deflections of a top within +/- 0.001″ which is very acceptable.

There are several stages in the guitar construction process where it makes sense to perform deflection tests involving the soundboard. The first test is done during the selection of the tone wood material as part of the criteria in making sure that we start with an optimal piece of tonewood. The next is done before the braces are added to the soundboard in order to determine an optimal starting thickness for the top. The next is done during the final thicknessing and brace shaving step of soundboard tuning (which is what this blog article is about). The next one is done after the bridge is added to the soundboard. Finally, as the instrument approaches completion, the deflection caused by the tension of the strings is measured above and below the bridge and recorded.

Generally, the procedure we use for measuring and recording deflections is as follows.

Measuring the deflection from a weight placed at various points on a grid placed over the soundboard.

Before we start the deflection tests for the final thicknessing and brace carving stage of construction, we create a very thin paper template with a 1″ x 1″ grid on it which we place over the soundboard so that it is protected from scratches and dents. We use a very thin paper which we tested to confirm that it does not affect the deflection values. Initially we perform a full set of measurements before the bridge is attached to the soundboard.  Once the deflection measurements are taken, we normalize them based on a standard force value of 2 lbs. This is done so that data can be compared with values taken by other luthiers (as proposed by David Hurd).

Next we use a contouring program to map the deflection values for the entire soundboard.

Contour Map of Deflections produced by one of several free contouring applications available on the Internet.


This map is then reproduced on the full size Grid template.

Contour Map - Full Scale for Use in Tuning the Soundboard Braces

This sheet is initially used as a guide for where to take the deflection values and after the data is contoured, it is used as a guideline along with Chladni patterns in tuning the soundboard by adjusting the plate thickness and by adjusting the height and thickness of the braces.  This is an iterative process.  We carefully carve and adjust thicknesses and then take deflection values and perform Chladni tests again. 

Chladni Pattern of 2nd Mode for the German Spruce Soundboard

This pain staking process is repeated until we reach the pre-established guidelines we have worked out regarding the deflection pattern that we want in the final product. It is these guidelines that each luthier must develop and refine as part of their artistic contribution to this process. This allows us to achieve the ultimate balance between strength and the tonal quality we are wanting to achieve for each guitar. There is a lot of work and time involved in doing this but the payoff in a masterfully constructed hand crafted classical guitar is well worth it. I wanted to write this article so that our customers know how much care is taken to be sure the value of these guitars far exceeds the cost and that each Wood Ring guitar is truly an investment that is built to give them a lifetime of enjoyment.

 Links of Interest

Wood Ring Guitars – Unique Hand Crafted Guitars for Exceptional Musicians. Dallas, Fort Worth, Weatherford, Texas.

Left-Brain Lutherie by David Hurd –

David Hurd’s Ukulele Website –

Review of David Hurd’s Book – Left-Brain Lutherie

Quick Grid – Open Source Contouring Program

Of Science, Art, and Society Blog Entry on “Reading Tea Leaves to Predict the Future – Using Chladni Patterns to Create Extraordinary Classical Guitars”


The Science and Art of HDR Photography


There are very few arts that have had as much influence from science on their creation and improvement as photography.  Having done photography for many years now, I feel that I understand the basics of good photography. I have studied the amazing features of my D700 Nikon DSLR camera and understand how to use them well enough to get a good photo under varying conditions. I have studied composition, lighting, exposure, color and many other topics that are important to good photography.

Even after mastering the aspects of photography, there are still many scenarios where what I see or what I want to emphasize in a scene is considerably different than what is produced by taking a single photo. This is because the relatively simple mechanism by which a camera works cannot reproduce what the human eye working directly with the brain can. For instance, when it comes to capturing and processing scenes of high contrast and widely varying areas of light and darkness, the biochemical and neurological processes which lead to sight are far superior to a simple mechanical aperture exposing some film in a camera (or a photosensor in a digital camera).

Three exposures of some trees and a sunlit cloud. None show the way the scene really looked.

 Until recently, unless you had access to sophisticated and expensive film processing equipment and the considerable time and knowledge required to use it, your only alternative was to say “you had to be there to appreciate it“.  Since the early 1800’s, when photography was invented, photographers have worked very hard to reproduce what they see in their mind’s eye and have used a myriad of techniques to do this. Because of the cost, expertise and time involved, these techniques were not practical though for anyone but the most accomplished of professional photographers. That has changed.

With the advent of the personal computer, the digital camera, and ever more sophisticated image manipulation software applications, almost anyone with some time and a little study can learn to adjust images taken on their digital cameras, including those with highly varying light and dark areas, to produce first class photos. Now you and I can recreate those scenes photographically that previously required the image plus an embellishment of verbal descriptions of how beautiful it was to get the point across. This technique is called High Dynamic Range Photography or simply HDR.

A more realistic image created from the three exposures using HDR photography techniques.

 What is HDR Photography?

HDR photography is a method of combining different exposures of the same scene to allow the photographer to capture a wider range of tonal detail than could be captured by a single shot. Since photography was invented in the early 1880’s, one of the classic problems that photographers have faced was creating a photo that was representative of what the eye could see in scenarios where the shot included areas of intense lighting as well as very dark areas. In such shots the resulting photo might show adequate detail in highly lit areas but the darker areas would all be very dark or black with little or no detail. Alternatively the shot might show detail in the darker areas but the lighter areas would be washed out with little detail.

 Camera vs the Human Eye

Three exposures taken of a poorly lit room which were used to create a composite image using HDR photography.

Dynamic range for a camera can be described in terms of Exposure Value differences between the brightest and darkest parts of an image. In a camera, a combination of the shutter speed and aperture setting controls the exposure.  One purpose of the aperture of a camera is to control the amount of light that is allowed to enter the camera. This limits the brightness of the image by restricting the size of the aperture to stop some of the light from entering the camera. Rather than allowing continuous control of the aperture size, cameras allow the photographer to increase or decrease the size of the camera’s aperture in discrete steps. These are called stops. As you go up the stop scale for a camera, each stop allows 1/2 the light intensity to enter the camera as the previous stop. I did a survey of several photography oriented websites and the consensus regarding the dynamic range of cameras vs the human eyeball measured in stops are as follows. Most point and shoot compact cameras have a dynamic range of 5-7 stops. Most high end SLR cameras have a dynamic range of 8-11 stops. The human eyeball static dynamic range has been estimated to be between 10 to 14 stops.  Given a minute or so to adjust, the human eye can see a total dynamic range of approximately 20 stops.  This is much higher than even the best SLR camera image.

Why do we see more dynamic range than what is shown in the photos we take? It mostly has to do with our brain’s interpretation of the image transmitted to it by the eyeball. The brain and eyes work together in real time to evaluate multiple exposures in a continuous way such that the mind’s eye sees an image that is far superior to what the camera is mechanically capable of capturing in a single moment.

Interior room imaged processed through HDR techniques has much better lighting characteristics.

HDR Photography Can be Learned by Almost Anyone

Due to the great image manipulation tools that have emerged in the last 10 years, HDR photography can now be done by anyone with a camera with basic features like aperture and shutter speed controls. There are a couple of free software applications available for doing HDR.   For the better HDR software you will need to spend from $30 – $700 in software tools depending on how good you want the resulting images to look. Most of these tools offer a 30 day free trial if you want to try this out. There are lots of websites that explain how to do HDR photography in detail so I will just briefly go over the process based on some photography that I did recently that required HDR to make them look correct. For anyone that wants to learn how to do this in very detailed steps, check out the links at the end of this post.

 The Process

  1. Take at least three photos of the same scene but with different exposure settings. One will be taken at the “ideal” exposure for the scene as determined by a light meter or automatically by your camera. One will be taken one F-Stop below the ideal exposure to create an over-exposed photo. One will be taken one F-Stop above the ideal exposure to create an under-exposed photo. Most high end cameras allow you to do this automatically using a feature called automatic exposure braketing.
  2. Move the images to your computer.
  3. Use an HDR software application to merge the photos and adjust the tone mapping using various controls to achieve the desired look.
  4. Correct various problems that are sometimes introduced in the process of merging the photos. Among these are (a) ghosting caused by things moving while you were taking the shots, (b) chromatic abberation caused by the camera lens reacting to different wavelengths of light by offsetting them in shots that were taken, (c) noise that shows up in some areas of the photo as pixels of various colors. There are automated tools that allow you to fix all of these.
  5. Save the image and post it to the desired medium.

The detail of the clouds and the beautiful colors of the foilage cannot be captured in the same image.


The examples included with this post include a landscape shot with some trees and a beautifully sunlit cloud, an interior shot, and a landscape with some menacing storm clouds. I have included three shots of different exposures for each along with the final HDR photo. For the shot with the trees and the brightly lit cloud I was able to show the beauty of the cloud with the orange highlights from the late afternoon sunlight while lighting up the trees so that they didn’t show up as a bunch of dark shadows. For the interior shot I was able to use HDR photography to enhance the lighting in the poorly lit room without having to use a bunch of expensive lighting equipment.  For the landscape with the menacing storm clouds I was able to bring out the details and textures in the clouds while still being able to show the color of the trees. It takes a little more time and work to do this but as you can see it is worth it to get a final image that represents pretty much what I saw with my eyes.

With HDR techniques we can capture both the cloud texture and the beautiful foilage colors.

Still a Way to Go But We’re Getting there Fast!

Even with the amazing technology of HDR photography, it is still not quite as good as the eye can see. The physical mediums that we currently use to view photographs like film, high resolution monitors, etc. do not have the dynamic range of human sight. To resolve this issue, HDR techniques currently reduce the range of contrast for the photo while allowing more detail to be seen in the brighter and darker areas than in a traditional photograph. This results in some darkening up the brighter areas and lightening of the darker areas. This means that a really good HDR photograph is tuned to the medium that it will be displayed on. As time goes by though, improvements will be made both in image manipulation capability and in the output media to increase the dynamic range of what can be displayed.

We are already seeing cameras come out with an HDR mode that allows the photographer the option of doing HDR photography in real time with no post processing. The i-Phone 4 was one of the first devices to offer this option on its camera and it works reasonably well considering all you have to do is point and shoot. Now all the major digital camera manufacturers have at least one camera model that offers this feature. Still, if you want to be able to produce amazing HDR photographs on the order that some of the best HDR photographers produce, you will need to invest in a good digital SLR camera as well as some of the software mentioned below and spend some time learning the techniques involved. To me it is certainly worth the investment in both time and money.

Links of Interest and Further Information

Photography Basics – Photography Basics Article  – Offers a good discussion of the basics of good photography.

LifeHacker Article – How a Digital Camera Works

Photography Basics – A very good photography basics article.

Digital Photography School – A good site with tutorials. Also allows you to submit photos and get the critiqued and to write articles.

The Luminous Landscape – One of the web’s most comprehensive sites devoted to the art of landscape, nature and documentary photography using digital as well as traditional image processing techniques.

The following are four good posts from the same website.

Digital Photography Basics: The Camera

Digital Photography Tips for Beginners

20 Must-Reads for Amateur Photographer

Top 8 Photography Websites

Great Image Software Tools for Producing HDR Photography.

Top 10 HDR Applications for 2011

Essays on What the Eye Sees vs What the Camera Captures

HDR Photography Tutorials – One of the better HDR tutorials on the Internet.

19 Good Tutorials for Doing HDR Photography


Summer of the Hawk

Hawks of Summer 2011

Birds have fascinated me and my family for many years.  We have had a Double Yellow Headed Amazon Parrot as a pet for over 20 years.  We have always named our computers after bird types.  Our consulting company’s website ( uses various types of birds as a metaphor for traits necessary to be successful in the use of computer technology to meet your business goals.  Sandra has been inspired by the subject of birds in her artistic endeavors.  An example line drawing of a hawk drawn by Sandra is shown at the end of this post.

A mother Cooper's Hawk looking down at her newly hatched babies in the nest.

You can imagine our pleasure when this summer my family and I had the unique privilege of having a pair of Cooper’s Hawks build a nest at the top of an oak tree in our front yard. Within a few days after the nest was completed, it was apparent that the female had laid eggs in the nest and was sitting on them. After a few more weeks we began to see a behavioral change in the parents. While the female stayed on or near the nest most of the time, the male was constantly out hunting for food. After a couple of more days of observation we began to see little downy heads popping up from time to time, especially when one of the parent birds showed up with a mouse or a lizard for dinner.

It became a daily ritual in our family to check on the hawk nest. As days passed by the baby hawks were rapidly growing. We were able to see more and more of their heads and their gaping mouths as they made themselves available at feeding time. After a couple of weeks the female joined the male in the hunt for food for the demanding chicks. They were extremely dedicated parents, working from sunup to sundown to bring sustenance to the baby birds.

If you do a search on the word “hawk” or “hawk science” in Google or Bing, you will find the search results page littered with aerospace engineering companies, NASA missions, and military hardware or possibly news about a sports team. The very nature of the hawk’s natural abilities evokes a strong symbolism that is appealing to organizations like sports teams or the military. In earlier times, hawks and eagles were symbols of strength and wisdom to Native Americans. Their feathers were used as symbols of social standing and achievement in the tribe. Hawks are swift and alert. They have keen eyesight. The shrill call of a hawk sends smaller creatures scurrying for the safety of shelter. Little did we know that we would be able to observe these qualities and more in the family of hawks that lived in a tree in our front yard in the summer of 2011.

From Crisis to Opportunity

Baby Cooper's Hawk had fallen from the nest into the front lawn.

One hot morning in late June something unanticipated happened. Sandra went out into the front yard to view the nest and found that one of the baby hawks had fallen to the ground. He was lying in the shade in a patch of St. Augustine grass that covers much of our front yard. As she approached the baby bird to determine his status, she found that although he was unable to fly, he was able to walk around on the ground. He seemed to be ok despite falling at least 30 feet! She immediately came back inside the house and informed me and Aaron about the situation.

After taking a look at the small helpless hawk, many questions started racing through my mind. How is this helpless bird going to make it? Will his parents come down to the ground to feed him? How will he survive the hot Texas days on the ground. We had already had 20 days of 100+ degree rainless weather with no relief in sight. Even if he could survive in this harsh environment, how would he escape other predators now that he was in the worst place possible for a baby bird – on the ground.

Baby hawk being coaxed onto a stick so he can be placed back into a tree.

We realized that there was only so much we could do to help. We immediately decided to try to get him off of the ground. I went and got a pair of heavy duty leather gloves and approached the baby hawk. He tried to run but immediately decided he could not escape me so he hunkered down into the grass, opened his wings as wide as possible, and opened his mouth in a threatening gesture. I carefully folded his wings back down over his body and gently grabbed him. I took him over to a low lying branch of a smaller tree and placed him on the branch. Initially he was reluctant to grab onto the branch but after a couple of tries, he did grab on and maintained his balance. He stayed there for the remainder of the afternoon and into the evening. As darkness moved in, I thought to myself that it will be a miracle if he makes it through the night.

Baby hawk after being placed back on a tree branch.

We woke up early the next morning and looked out the window, wondering if he would still be alive. Sure enough, there he was, in the exact same place that we had left him the night before. At least he had sense enough to stay put. Somehow he had managed to avoid detection by predators of the Texas night like cats, raccoons, opossums, snakes, and owls. At first we were extremely happy. We had thought the bird’s chances were very slim and that it probably would not survive the first night. Now that he had survived, a new reality began to sink in. We realized that it would take days if not weeks for this bird to mature enough to fly. How was he going to survive the hot Texas days without nourishment and water? Then it happened. The baby bird began to call out a familiar sound. It was a loud shrill whistle srr-sssrrrrrr. We saw a parent bird circling the area. The baby was calling to its parents. The circles became smaller and smaller as the bird flew lower and lower. Then it landed on a tree branch just above the baby bird. Finally it flew down next to the baby bird and began to feed it what looked like a piece of a small reptile it had caught.

Over the next three weeks this process continued. Both parent birds were involved. One would stay fairly close to the area while the other would go out hunting for food. The parents worked very hard taking care of the birds in the nest as well as the one who had fallen out. It was amazing to see how dedicated these two parent birds were in taking care of their young. They very quickly adapted to the situation. We had a heart felt sense of amazement to be able to witness this.

Ground School and Flight Training

During the course of the next three weeks, the baby bird bailed out of the tree onto the ground several times. We tried to not interfere except when it looked like the baby was wandering into harms way. For instance the tiny hawk tried to cross the hot asphalt street during the busy part of the day. We grabbed it and put it back into the tree before it was inadvertently run over by a neighbor as they were headed home from work. By this time, Aaron had refined the process by getting the baby bird to step onto a parrot cage perch. This was less trauma to the baby bird with less risk to the person (the baby bird was growing rapidly and the beak and claws looked very sharp and menacing).

We did observe that after a three week period, the baby bird finally started making short flights, although we did not see if fly. We speculated that he was able to fly because we would leave him sitting on the low lying branch that had been his home for over two weeks. When we went back out later in the day to see how he was doing, he was gone. Looking around revealed that he was on a branch of the same tree which was five or six feet higher. We would also find him on low lying branches of other trees in the front yard. All throughout this time his parents continued locate him and feed him.

Also after about three weeks after the baby initially fell from the nest, the baby bird’s siblings began to leave the nest. One in particular made a habit of flying down and sitting next to its smaller sibling. At first we thought that the larger bird came down to keep his smaller sibling company, but it also made it more likely he would be fed more often because it was easier for the parents to feed the two birds when they were sitting so close to one another.

The larger chick came down to join its smaller sibling on a lower tree branch.

After another week or two the baby bird increased its mobility until it eventually worked its way back up to the nest and beyond. The hawks stayed in the area for another month or so as the babies learned to fly. In mid August we were blessed with a nice rain storm after months of heat and drought. The resulting gusts of wind were a perfect training exercise for the baby hawks. We spent at least an hour watching the babies following the parent birds as they rode the air currents several hundred feet in the air and then did practice dives toward the tree tops. It reminded me of my childhood dream of wanting desperately to learn to fly like a bird.

As time progressed, the baby hawk moved higher up into the tree top canopy.

After another week we noticed the hawks were gone. Sometimes we could hear their calls in the trees down the street but even this ceased after a couple of days. The only evidence that remains is the large nest that still sits at the top of our oak tree in the front yard. I don’t know if they will be back next spring or not. I hope so. Nevertheless, in the future, when I think of the year 2011 I will always remember the Cooper’s hawks that chose to raise their family in a way that allowed us the amazing experience of being able to observe their way of life so closely.  I have a new found respect for the intelligence and instincts that nature has given these beautiful creatures to successfully raise their young.

One of our last photos of the young Cooper's Hawk calling to its parents for food.


Other Great Resources

Birds in General – Lots of information about birds and bird watching around the world.  Contains lots of information about birds in general with many excellent links for further study. – A great resource for bird watchers in Texas. – Website of the Texas Ornithological Society. – A list of all the types of hawks found in Texas. 

Hawks – A website that has many excellent links to sites about hawks and other raptors. – Everything you want to know about Cooper’s Hawks and more!

Birds and Art

 – A short essay on art inspired by birds. – An interesting website done by that is dedicated to the birds of Stanford.  It emphasizes both the science and art associated with birds. – A website dedicated to the art and science of hawks.  Excellent resource! – Some great photography of some Cooper’s Hawks and their babies on Martha’s Vinyard.


Good Morning Rainbow

Rainbow across the morning sky.

Sandra came in from retrieving the morning paper early today and exclaimed “Danny, come out. You have got to see this rainbow!” I quickly grabbed our camera and ran out to see what she was so excited about. She was standing out in the front yard and pointing toward the western sky. I looked and arching up above the oak trees was one of the most vivid and beautiful rainbows I have seen in quite a while.  This was not expected because there were just a scattering of clouds across the sky with no rain in the forecast.  Nevertheless it was a wonderful sight to behold.

Birds flying across the rainbow in the sky.

 The Size of a Rainbow is Relative to the Sun’s Angle

This rainbow had some beautiful qualities. The arc was quite steep (almost vertical at the base on the horizon) and the top of the rainbow was very high in the sky. It turns out that this is due to the fact that it appeared early in the morning. The Sun was near the horizon and the Sun’s visible light rays forming the rainbow were nearly horizontal. The arc of a rainbow that occurs at sunrise or sunset appears to be larger that one that occurs when the sun is higher in the sky. The apparent height of a rainbow decreases as the height of the sun in the sky increases. When the Sun exceeds an angle of 42 degrees above the horizon no rainbow can be seen by an observer on the ground.

Another view of the rainbow arc across the morning sky.

Morning and Evening Rainbows

Also the composition of the sunlight that reaches earth at sunrise or sunset generally has more red hues and less blue hues. This is because of atmospheric scattering of the sunlight due to dust, smog, and water vapor in the air. It is more prominent in the mornings and evenings because the light passes through a longer stretch of atmosphere at those times than it does when the Sun is higher in the sky. This affected the color of our morning rainbow by emphasizing the bands on the red side and muting the bands on the blue side. You can see this emphasized even more by the color of the clouds in the photos. We were certainly the benefactor of these phenomena and I am grateful that Sandra observed this beautiful rainbow and called it to my attention.  The affect of the Sun’s angle on rainbow geometry and color has been understood since the 1600’s. The phenomena is explained in more detail in this post on Rainbow Angles.

A Sight that Evokes Happiness

There is something about rainbows that makes most people feel good.  A rainbow is an elegant and sweeping display of color across the sky.  It is amazing to me how quickly nature can summon up the ingredients and conditions necessary to form the pallette of visible colors that we humans can see. Viewing a rainbow is a fleeting experience. After five minutes the rainbow quickly dissappeard as the Sun rose. I can certainly tell you that this sight put a smile on my face and gave me a great feeling of happiness.

The Science of Rainbows

The science of rainbows is fairly simple and is taught to most of us in elementary school.  All it takes is the Sun shining across some water droplets suspended in the atmosphere. In order to see the rainbow, the viewer of course must be in the right place in relation to the Sun and the water vapor. The water droplets act like a huge prism and through refraction and dispersion of light, the droplets break the sunlight down into its component freqencies forming the band of colors of the rainbow.  We commonly say that a rainbow is comprised of the colors Red, Orange, Yellow, Blue, Indigo, and Violet.  Historically these component colors of a rainbow were first identified by Isaac Newton. In reality, a rainbow is a continuum of light frequencies that extends from the infrared to the ultra-violet frequencies and includes the entire band of frequencies that humans percieve as the colors of the rainbow.

Nature’s Art

With this post we are creating a new category called Nature’s Art.  From time to time we will be posting many more articles to this category as there are an infinite number of instinces where Nature either inspires art or is a naturally occurring art form in and of itself.

 Interesting Links

  • The Wikipedia article on rainbows is very good. It describes the science of rainbows, the scientific history, and the cultural influence the rainbow has had.

 There many websites that explain very effectively how rainbows work.

  • There is a very nice interactive app on the National Taiwon Normal University website that effectively demonstrates the physics of rainbows.
  • The Watching the World Wakeup blog has a good post called How a Rainbow Works which is worth looking at.
  • The site How Rainbows Happen explains all the physics concepts required to understand how rainbows happen.
  • This web page called Rainbow Physics explains very simply how a rainbow works. It was posted by a photographer and has some good rainbow photos. It is one part of a 5 part series on how to photograph rainbows.
  • This website has some Interesting Rainbow Facts .



Reading Tea Leaves to Predict the Future

Using Chladni Patterns to Create Extraordinary Classical Guitars

It may seem surprising to see this in a blog dedicated to Science and Art but it is true. My son Aaron and I regularly use tea leaves to predict the future! We are not seeking the winning numbers of the next Lotto Texas drawing, how Aaron’s romantic interests will play out, or whether it will rain next Sunday night (although that would be handy information). You see… instead of being a tasseographer, who seeks to predict the future by using superstition and folklore, Aaron is a luthier who uses science to make predictions about how his hand crafted classical guitars will sound. He is also a classical guitarist. He knows what he wants to create both visually and aurally. He knows how the guitar needs to feel in a guitarist’s hands. Yet even with all these artistic skills there is more to know when creating a high end classical guitar. Lutherie is tedious time consuming work and one mistake or bad judgment can cost you six weeks worth of time and hundreds of dollars in material costs. The bottom line is that Aaron wants to be able to know with some degree of certainty that as he carves, sands, scrapes, shapes, assembles and configures the components which eventually become a beautiful classical guitar, it will also be the best sounding instrument possible. This is where the tea leaves come in.

 How a Classical Guitar Works

Strings transfer vibrational energy to the soundboard.

The amplification of the vibration of the strings on an acoustic guitar is caused by a transfer of vibrational energy from the strings to the soundboard (the top plate to which the strings are attached).  From there it is transferred into the resonant cavity formed by the body of the guitar and into the air in front of and around the guitar. These components act very much like a loud speaker but are more complex because not only do they amplify the sound vibrations, they also add harmonic overtones which the listener interprets as the tonal quality of the guitar. The back of the guitar also contributes to the amplification to a lesser extent. All the components used in a guitar contribute to many other acoustical properties of the guitar like tone, sustain, harmonics, etc. It is the careful manipulation of several design parameters that allows Aaron to create the impressive beautiful sound of a Wood Ring guitar.

 Testing and More Testing

Testing is an essential part of the process of creating an outstanding classical guitar.

There are many processes and tests that we perform throughout the process of building each guitar that guides us toward the final great sounding product. Initially there are several tests that are used to evaluate each piece of wood being considered as a component of a guitar. Not only must the wood be visually appealing, it must have properties that are conducive to the production of the sound Aaron is looking for in his guitars. For instance, he is looking for pieces of wood that have a high strength to density ratio. This has to do with the need for the guitar to be light as possible in the hands of the player and yet strong and durable. A high strength to density ratio also allows stronger and longer lasting sound production with less energy input from the player.  He is also looking for wooden components where the internal damping of sound is minimal. This means that when energy is put into the guitar to make it vibrate, that the loss of energy to heat through internal friction is minimized.

 As construction proceeds, tests are done to guide us at each stage of construction toward the finished product. One test that we rely on is a process called Chladni testing of the soundboard. Of all the components of a classical guitar that the luthier creates, the soundboard arguably has the most influence on how the guitar sounds. The magic is in how the soundboard responds to vibrations. Sound vibrations transferred to the soundboard (either by guitar string or by loud speaker) occur as standing waves across the two dimensional surface. Since the vibrations are fast and the amplitude of the waves are very small, we must use an indirect way of seeing them. This is where the tea leaves used in conjunction with Chladni testing comes into play.

Graph showing the oscillating nature of a sound wave.

Great care is taken in the selection of the tonewood to be used as a soundboard as well as in the construction of the soundboard. We use Chladni testing to help us visualize and identify the resonant harmonic patterns that the soundboard favors. Every piece of wood used as a soundboard favors certain sound frequencies. The complete set of frequencies that a soundboard favors is like a voiceprint. It is a unique acoustic signature for each piece of wood used. It is the luthier’s job to evaluate and manipulate these signature frequencies to create a soundboard that brings out the full potential of the piece of wood that becomes a soundboard. It is the combination of these favored frequencies that experienced luthiers listen to when they tap on the wood to hear the wood’s tap tone. It is also the manipulation of these frequencies throughout the building process that helps the luthier create the optimum sounding guitar.

 Chladni Patterns

This Chladni testing process takes advantage of a phenomena called Chladni patterns. These patterns were discovered by a man named Ernst Chladni (pronounced Klahdnee) (1756-1827) who was a German physicist and musician. He has been called the “father of acoustics” because of his major contributions to the study of sound. He discovered that by drawing a violin bow across the edge of a thin plate of wood it would vibrate. When he placed some sand on the plate, he was able to create patterns by creating vibrations at different frequencies. Different patterns were created depending on the shape of the plate. See the images below.  The rectangular plate images of Chladni patterns were created by John Tyndall in 1869.  The circular plate images are from Chladni’s work on the subject.

Chladni patterns for rectangular and circular plates.

 The geometry of instruments like the guitar and violin generate patterns similar to both rectangular and circular plates. Different types of materials produce differing patterns as well. We have found that different species of woods can produce dramatically different patterns as well for a given shape. There are many variables that can affect the patterns during the testing process as well. Things like speaker location, how and where the plate is supported must be carefully controlled during testing so that repeatable and comparable results can be recorded and analyzed.

What is important to the luthier is that these patterns demonstrate visually how the sound waves travel through the plate. The places where the sand remains are the nodes of the wave pattern (where there is no vibration). The places where there is no sand are the anti-nodes of the wave pattern (where there is vibration).

Violin makers were some of the first luthiers to use this phenomena to fine tune their instruments. This process was documented in an article of Scientific American written by Carleen Hutchins a renowned violin maker who made huge contributions to the science of plate tuning of violins using Chladni patterns. This article described how these patterns can be used to guide the manipulation the top plate thickness to get an optimal sound.

Tests Performed in Crafting a Wood Ring Guitar

Our testing apparatus consists of a stand that we built for this specific purpose. It is based on a design described in the book called “Left-Brain Lutherie” by David C. Hurd, Ph.D.  David is a master at building Ukuleles. His book is a classic with regard to using the scientific method in the construction of stringed instruments. The guitar plate to be tested is placed on two tightly strung rubber bands one supporting the plate on each end. A speaker is placed under the guitar plate and is driven by a computer program which produces tones at any frequency the user desires. We place tea leaves on the plate to show the patterns. Sand, salt, glitter and saw dust have all been used to create Chladni patterns but we have found ground tea leaves to work very well for our purposes.  The full range of frequencies that a guitar can produce are scanned and the frequencies of the patterns are recorded along with the geometry of each pattern.

 The following is an image of some Chladni patterns we found for a rectangular piece of German Spruce that we will be featuring in a guitar Aaron is currently working with. This is a representative set of quality control tests that we perform on all pieces wood being considered as a soundboard for a Wood Ring guitar.  As you can see, the higher energy frequencies produce more complex patterns.

Chladni patterns recorded for a German Spruce wooden plate being considered as a soundboard.

 As the building process proceeds we again perform more Chladni pattern tests on each soundboard. We identify certain dominate patterns over the frequency range of the guitar that we can follow throughout the building process and watch how their absolute frequencies change as well as how their relative frequencies change. This information guides Aaron in the actions he needs to coax each guitar toward the sound he is seeking. The photos below show some of these patterns.

Chladni patterns of German Spruce soundboard before attachment to sides.

Chladni patterns of Western Red Cedar soundboard attached to guitar sides.

Thank You!

There are many luthiers that use the process of Chladni testing to create the outstanding guitars that are made around the world.  No one learns something this complicated without some help. Some of the luthiers that greatly influenced Aaron’s learning process are listed below. We wish to thank them for having the self confidence and generosity to share some of the knowledge they have spent so many years to develop so that others may stand on their shoulders to take lutherie to the next level.

Brian Burns – Brian’s website was influential in helping shape our testing program.  He has always been very encouraging in our correspondence with him.  Brian does consulting and also has some very nice lutherie tools for sale at a reasonable price.

Ervin Somogyi – A class act with regard to lutherie. Many of today’s luthiers have learned from Mr. Somogyi.

Luthiers of North Texas (LINT) – This is a group of luthiers who meet every two months in the Dallas – Fort Worth Area.  One member in particular, Derek Lambert, is a very good friend whose ideas, feedback and conversation in general are all greatly appreciated.

Classical Guitarists

There have been many fine classical guitarists in Texas that have been kind enough to play Aaron’s guitars and give him very candid and valuable feedback as to what they are looking for in the ideal guitar.  There are a couple that we would like to give special thanks to.

Fernand and Olga Vera – These are two dear friends that are amazing classical guitarists. Be sure and see them in concert or when they are playing at many of the local guitar festivals. Also don’t miss a chance to attend their annual workshop.

Mitch Weverka – Mitch heads up the Fort Worth Guitar Guild and has been a catalyst for promoting classical guitarists in the Fort Worth area. He also heads up the Fort Worth Guitar Guild. We are grateful to him for all the great feedback.

Interesting Links

Cymantics – A branch of science emerged in the 1960’s called Cymatics. It is the study of visible sound and vibration. This is a field of study which was named by Hans Jenny emphasizing the intersection between art and science in the study of unseen phenomena like standing waves in various types of media. 

TED Presentation About Cymantics by Evan Grant – A wonderful talk at the TED conference in July 2009 given by Evan Grant about Cymatics (the study of visible sound). It has some great demonstrations of Chladni patterns and how this study of the substance of things not seen is being applied in research around the globe. It is for instance being used to create a lexicon of Dolphin language and is also allowing artists to create wonderful art from different music sources from Beethoven to Pink Floyd.

How Guitars Work – Describes how classical and acoustic guitars work.

Wood Ring Guitars – Last but not least!  Don’t forget to visit the Wood Ring Guitars website.  Please contact Aaron Ringo to explore the possibility of having a custom hand crafted classical guitar made to your exact specifications.  We also have several very nice guitars in stock.  You will be amazed by the craftsmanship and sound.

     Copyright © 2011-2012 by Danny and Sandra Ringo.  All rights reserved.  Articles may not be reproduced without permission.