The Soundboard of the Piano

During the time when the piano was going through much scientific development to establish "standard" designs of its various components, or to put a time frame on it, going back to the nineteenth century, the development of the soundboard was going through experiments of the empirical kind because at that time there was precious little solid scientific information on which to base soundboard construction. So we find ideas such as the wave theory that supposes the piano's tone quality and volume is dependent on the design of the soundboard. According to this theory, the soundboard shapes the sound wave transversely so as to give a piano its distinct sound, relegating all other factors such as hammers and strings to secondary status, if that. Another theory purports that the soundboard produces waves that travel through the air as compressions and rarefactions, or in other words, as longitudinal waves, being driven by the strings. No coloration of tone is possible by the soundboard since no transverse waves would be produced.

Experiments were done using different materials for the soundboard, such as copper, iron, and other metals, with varying degrees of success. One may presume these were not subsequently pursued because of costs. One experiment used parchment as soundboard material which proved totally unfit. So wood was the ultimate material of choice.

Dolge in his book "Pianos and Their Makers" wrote of experiments carried out at the Mathushek factory during the years of 1867 to 1869 which were done to find out how thick a soundboard needs to be to be most responsive to the string vibrations. The experiments consisted of using various thicknesses of soundboard panels from a full one inch to three-sixteenths of an inch, and trying varying tapered thicknesses within boards. All kinds of variations to the ribbing were also tried. In the end, the report was that the most satisfactory board was three-eighths of an inch thick in the treble, tapering off to one-fourth of an inch in the bass. The ribs were placed practically equal distance from each other, tapering to somewhat closer together in the treble. All this pointed up the fact that the most important reason for good tone in a piano is the stringing scale and hammers. The importance of the soundboard as related to tone is shown solely by how faithfully it transfers the sound from the vibrating string into the air.

Although these experiments were done in the late 1860's, many other experiments were done by other makers, and you will find various numbers of ribs and configurations in pianos throughout the late 1800's. By the early twentieth century, rib patterns settled down to a fairly consistent standard of 10 to 14 or so ribs per board, depending on the size of the piano, fairly equi-distant from each other to somewhat closer together in the treble, as per the Mathushek experiments. Rib dimensions are thicker in height in the middle and less so at the ends.

There have been, of course, successful soundboard designs that deviate from the standard layout, but no substantial improvement over the traditional soundboard has yet come about by such designs. And there is still a wide open field as to what soundboard material might be used as an improvement over the traditional spruce wood. This would, however, necessitate changing the design and layout of a spruce board to suit the new material to a greater or lesser degree, but that will necessitate much experimentation on the part of the designer. And to what end? To possibly have a piano that will not be affected as much by atmospheric changes? But at what cost? It is certainly not an area that will yield any sort of enticing return for the experimenter, that is certain.