...It is easier to compare one wood tap sound to another, than say, a tone generator sound to a wood tap.
...The frequencies here are from about 220HZ to 810HZ in steps of 10 HZ. This provides a tool that can estimate a wood tap tone to within +- 3HZ (with a lot of practice.)
...Changes in humidity do have a slight effect on frequency (as much as 5hz.), but since all the strips change relative to each other, it provides a useful guide. (remember that the wood you are tapping is probably also affected by a similar amount.)
...Through one of these points, a small hole is drilled and a finish nail is pushed through into the support. The hole is slightly larger than the nail to allow free movement. The other support point of the tone block also rests on a narrow felt pad placed at just the right position.
...The tone blocks are positioned so that the front ends are even. You will notice that on the back side, the end lengths vary considerably.
These were pieces I had around my shop.
...Try and pick out wood that is musical, or lively to a tap.
...Cut all the pieces the the same dimension and quarter sawn with the growth rings vertical (up and down).
...The species of the wood is not the most important thing, but it would be preferable to all be of the same wood variety if possible (mine are not).
...When doing final tuning, you raise tone by sanding the ends, say on a disc sander, taking equal amounts from each end until tone is correct. When the tone is slightly too high, then evenly sand (or plane) material from the bottom side until the target frequency is reached.
...Notice the pencil marks in 22% of the length of each piece from each end. These are the points where that strip needs to be supported both when test taping for frequency and when installed permanently. I use a strips of felt about 3/8" wide and across the strip which are glued to the supports which will pass underneath, across the tone blocks.
...The size of the woood blocks I chose are 13/16" by 13/16" and the highest tone blocks are 12 1/2" " long and the lowest pitch blocks are 25 " long.
...When complete, I sealed the ends of each tone block with a wax sealer to minimize moisture effects and to help prevent cracking.
Notice how the front ends of all the strips are positioned even across.
...Here I am spacing the tone blocks out evenly (the back joint is pinned with the nails pushed into place already). I want all the blocks to be joined together but still be free to vibrate, SO.....
...Thus when in positon, one can allign all the blocks of that row by moving the outside (end) blocks back in line.
...I find that its reference use along with the HP sound analyzer help eliminate mistakes in the very tricky business of hearing and adjusting tone taps on wood parts.
...First identify the 'color' of the sound your are trying to find, comparing it to tones from different areas of your sonidecifer and when you have identified the right 'neighborhood' you can then begin comparing tones slightly above and below until you are very close.
...When comparing the final tone to your wood block references, you can then estimate that it is closer to this one than to that one and give an estimate within +- 3 HZ of the actual frequency.
...Now use your HP sound analyzer with your suspected correct frequency set in and see how the screen plot compares.
