Useful tools for Sound Adjustments...
...The tools I will describe are those that will be aids in hearing tap tones so you can make good adjustment decisions.
...First a word about how our ears hear and compare two different sounds,( pitches, or frequencies). Primarily our ears hear harmony relationships. If the two sounds are an octave apart, they will sound the same; if they are a fifth apart they will sound in harmony and may easily be identified as being the same pitch (frequency); the same is true of other harmony relationships. So........ The first rule in using tap tones to compare two different wood objects is to listen for what I will call "the color of the sound". Even seemingly identical violin wood parts of the same wood, and purchased at the same time may be a whole octave apart (that is one piece has twice the frequency of sound as the other), so before one can arrive at frequency comparison or identification, one must begin by identifying the "family or region of the sound frequency"; and ignore (for the time being) whether the first sound seems higher of lower than the second sound (tap) under investigation.
...My "SoniDeciFer" tool (latin for 'Sound Ten Maker') is very helpful for these sound determinations because it is a wood source to compare to a wood (tap) source. It also quickly allows one to determine the "family" of the sound. Once the "family" or neighborhood of the sound is identified, one can quickly zero in on the correct frequency (within say +/- 1 HZ) by comparing the tap under investigation to the reference tone bars, each of which is 10 HZ different in frequency to its neighbor, in the upper range, and 5 HZ different in the lower range.
...This tool is really just bars of quarter sawn wood about 1" square (the tree rings go up and down as viewed from the end) of varying lengths. The bars are adjusted so they tap precisely the frequency as noted on the ends. Notice how they go from 220 HZ to 810 HZ, in incriments of 10 HZ. (and now down to 120HZ). By tapping on the ends of the tone strips, one can quickly discover the area ("family") of sound that compares with our unknown tap sound.
...The bars are supported at 22.4% of their length in from each end on a strip of felt glued to the bottom side.
...They can be tapped either at the center or at either end.
..The virtual SoniDeciFer tool covers the range of 120-420HZ, which is the actual usable range for violin making.
...If wood were perfectly uniform, then we could just cut these wood blocks so they were all the same cross-sectional size (say 1" by 1") and then vary the length according to the formula (from an acoustical textbook), and we would have a set of reference tap blocks:
Frequency = height X (1/{length X length}) X squareroot of (the elasticity Modulus / density)
   The items to note are that:
(if the thickness is reduced 5%, then the frequency is also.)
(slight reductions in length make a large increase in frequency).
* Since the elasticity modulus and density are constant for any single source of wood (approximately), we can ignore these.
...Select wood that has good sound transmission properties (slide your hand along the edge of the wood you are considering to use; does the wood make a clear sound or is it muted and soft?) Cut identical sized (width and height) pieces quarter sawn and various lengths, according to our formula; then adjust them to their final frequency by sanding the top evenly to slightly lower the tone and sanding each end slightly to raise the tone. Support each block 22.4% in from each end on a strip of hard felt glued underneath. It is probably necessary to use a sound analyzer to measure the frequency of each strip so you can adjust them accurately. {A microphone and a personal computer driven sound analyzer program should work well enough though.}
22.4% of length
Two felt blocks
(end view...)
Finish nail through a slightly larger drilled hole in the wood sound strip, pushed into place.
Two support rails under felt:
(only one shown)
...In my opinion, this tool is vital for accurately working with instruments using a tap tone adjustment technique. First, I got my H.P. Sound Analyzer and then used it to make and adjust my SoniDeciFer sound reference wood bars.
...When tapping on a piece of wood, the 'tapper tool' makes a sound as well, so our ears must try and differentiate between the two tones; thus we want to use a tapper that adds little sound of its own, or is above or below the frequency of the wood we are trying to measure, that we can concentrate on the object of our attention, not the tapper.
...The knuckel of the hand is the best tapper of all; (Try the new newspaper pencil)
...The first knuckel of the finger is second best tapper;
...The eraser end of an ordinary wooden pencil the next best. (this saves on your knuckels and can get in much smaller spaces. The wooden end of the pencil is most useful if used carefully.
...{Using the fleshy end of the finger is useful as well when checking evenness of violin plates.}
...Wooden pencils often generate a lot of sound when they are used to strike another wooden object. Try and find a tapping pencil that gives a very dull 'thud' sound. This will make your ear much more effective.
..A Canadian friend (Mel Bosco) sent me a special pencil made of recycled newspaper. It seems to give excellent tap results (by far the best tap tool I have run across so far). they cost about $2 in Canada but are not available in the USA at this time. If you know someone in Canada who can order some for you and then send them on to you; this is the information;
'Smencils Gourmet ScentedPencils'...made from 100% recycled newpapers....... is their web site (they do NOT ship to the USA)

...The well respected violin maker Daniel Paris told me that the only sound analyzer he had discovered, that can analyze a 'tap on a piece of wood' is this one make by Hewelt-Packard in the 1980's {Model # 3582A}. He was kind enough to find me this used example which I purchased. The screen shows a typical frequency analysis of a tap on wood; all the various frequencies and how strong each one is. It does require some practice to begin to get usable results, but is often a good 'second opinion' when I am not sure of a tone. It is however the perfect tool for making and adjusting your own set of wood tone reference tone blocks with scientific accuracy.
... Now to get useful data from taps on wood with this H/P sound analyzer, there is only a narrow range of settings of the many disls and buttons which will produce good results. Please click here to see photos of the various sections for the settings I use.
...The next tool I want to tell you about is an Ultra Violet Light box. This is an adjunct to natural sunshine, for those days when the sun does not shine or when you want to subject a part to concentrated and even-all-over U.V. light absorption at the same time.
...It can also double as a warming box to get the wood parts up to about 100 degrees F. before gluing operations with hide type natural glues which require warm conditions for best results. For instance, my violin shop is unheated and it is helpful and important that the wood pieces I am going to glue together be about 100 degrees F. during the joining process (remember, the glue is at 150 degrees and the hide glue will gell if it cools suddenly).
...The design is basically just a wood box with insulation foam panels on the outside; a hinged lid, top sealing gasket.
...There are two light bulbs in porcelin sockets screwed to the sides at bottom on a house hold dimmer switch to control how much heat they make. Notice the pan of water in the bottom. This is to prevent a completed violin from drying and and cracking.
...The fluorescent light bulbs are special ones that give off high concentrations of Ultra Violet light. They are 24" long and 20 watt power on a standard house light switch. I have an external temperature gage mounted to track inside temperature.
...You may note that I have a counterweighted bracket to hang a violin on. The heavy duty aluminum foil (shiny side to the inside) is glued to the plywood structure with silicone caulking. This reflects the U.V. light evenly all around the parts.
...Any part that you want to protect from U.V. light absorption, you cover with aluminum foil. Do not let the fingerboard be exposed to the U.V. light as it might warp.
Bulb information: General Electric 24", 20 watt # 10244 / F20T12/BL
Marked on bulb: F 20 T 12-BL / Black Light / 20 watt
...Click here to see more details and photos of SoniDeciFer construction...
...A new virtual SoniDeciFer is available for free for you to download so your computer keyboard which will play the wood blocks. Click here for instructions...(2013)
(updated 2/2013)
...(2/2013) I now rely on the virtual SoniDeciFer that I down loaded off the internet, and then added the two sound files necessary to set up the programs on my computer (Just e-mail me and I will send them to you) and use it exclusively now.
..Get it at:
..The frequencies were determined in reference to my virtual tap tone tool and the best tapping tool is a special 'wooden' pencil made from recycled newspaper. I highly recommend you get yourself one or more. Company does not ship to the USA however. Cost is about $2 each in bulk, in Canada. See: "Gourmet Scented Pencils". USP code; 6 92046 92500 5.
...A special 'thank you!' to Mel Boszko of Canada who discovered these...these are by far, the best I have used so far.