does a Violin Work?
This is a question that all violin makers have asked over the centuries. It is an intriguing question that many people more experienced and knowledgeable than I have pondered and many answers have been presented over the five hundred years the violin has been in existence. How can an instrument so small and delicate produce such a wide variety of tone with such power? Under the fingers of a great player there is no instrument so expressive and so powerful as the violin. In this article, I will try to explain the fundamentals of sound production in the violin, but I am afraid the great mysteries will never be resolved and certainly not in this short article.
To understand the workings of the violin, we must take a imaginary journey into the sound box. But first letís talk a little about the wood. Traditionally, the violin is made of maple for the back, sides and neck, and spruce for the top. The spruce is a lighter, softer wood that has a different acoustical pattern than the maple. If the same wood is used, the vibrations tend to cancel each other out and you get a very dead sound. Think of a drum, the top is stiff and light, the body is hard. The same principal applies to a stringed instrument. In carving the top and back (often called plates) of a violin careful attention is given to the graduation or thickness of the wood, often down to a tenth of a millimeter. The top is graduated to about 2.5 mm except around the sound post area . The back is slightly different, thicker in the center and thinning towards the edges, much like a speaker that has a heavy metal center surrounded by thin fibrous material. Both in the violin and the speaker the heavy center creates momentum and movement throughout the entire plate.
Now we get to slip through the right f hole and slide down the sound post. We are standing on the back looking up at the arched top, the inside is bathed in a rich red light that is filtered through the thin wood and varnish. It feels like a miniature cathedral. As we look up at the ďceilingĒ, we notice the bass bar running directly under the left foot of the bridge. This acts as a beam for our arched dome, strengthening and stiffening the thin spruce top and distributing the vibration along the length of the top plate. The weight force transmitted through the bridge, about 20 lbs. when tuned to pitch, is supported on one side by the soundpost and the other side by the bass bar.
The tone of a violin can be so greatly altered by the position of the sound post that in Italian it is called the soul , or anima of the instrument. Roughly the sound post is placed just behind the treble side of the bridge. With the solid support of the sound post in this position the bridge is allowed to transmit vibration to the bass bar in a rocking motion. Thid rocking motion vibrates the bass bar along the whole top, thus increasing the vibration of the top plate and in turn resonating the air cavity and the rest of the instrument.
It is often thought that the sound post transmits vibration to the back of the violin and it does to some extent, but the majority of the vibration is through the bass bar and the air cavity. If you would like to experiment with this idea, you could drill some holes in the side of your violin, (well maybe not your BEST violin) and plug them with corks. Then play and remove the corks and notice the change in the tone. Well, maybe you donít want to do that with your violin. Fortunately, in 1963, J.C. Schelleng did this for us. His work is published in Research Papers in Violin Acoustics 1975-1993. He found a distinct reduction in tone and volume the more holes that were opened in the sides.
There are many factors that affect the final tone and quality of a violin. Type and age of wood, thickness of the plates, purfling, varnish, tailpiece, placement and size of the sound holes, type and age of strings, and many other factors too numerous to mention here. But the most noticeable have to do with the sound post, bass bar, bridge and thickness of the top plate. Building a violin is an adventure combining science, art and intuition.There are so many variables that the final result is always a surprise.The moment of truth when, after hours of work, the instrument is strung up and ready to play is very exciting. And now letís climb back up the sound post, out the f hole and put bow to string and see how it sounds!
Peter Van Arsdale is a local Berkeley violin maker.