THE SOUNDBOARD.
An Extract from "Pianos and Their Makers." By Alfred Dolge.
The science of acoustics as developed by Chladny, Tyndall, Helmholtz, and in its direct relation to the piano, especially by Siegfried Hansing, has given us much enlightenment as to the proper and correct laying out of a scale, also the laws controlling the production of sound by percussion and otherwise, but none of these scientists can advise as to the scientifically correct construction of the soundboard. The much coddled theory of "tone waves" found its, most obstinate opponent in the soundboard of the pianoforte, disproving forcibly almost every argument brought forward in favor of this theory. Not finding any assistance from scientists, the piano maker had to rely entirely upon empiric experiments, to construct a soundboard best adapted to his scale. All the experiments, and their names are legion, ended in coming back to the plain soundboard as constructed by the clavichord and harpsichord makers of the early days, namely, made of the best quality of well-seasoned fir, strengthened by bars or ribs glued on crossways. The various writers on piano construction differ materially regarding the importance of the soundboard in relation to tone development in the piano. The careful and learned Dr. Oscar Paul, laboring under the ban of the "wave theory," insists that the soundboard is the very soul of the piano and that tone quality as well as volume depend altogether upon its construction. Indeed, he holds that the tone is produced by the soundboard and not by the string.
Siegfried Hansing in his book, "The Pianoforte and Its Acoustic Properties," shows the fallacy of this contention beyond contradiction. He bases his argument on Pellisow's proven doctrine that the ear does not perceive sound thru so-called tone waves, but because of the shock or jolt by which the sound is created. Consequently, Hansing looks upon the soundboard as a drum, upon which the vibrations of the strings, caused by the striking of the hammer, are delivered as shocks or jolts.
Hansing disclaims the existence of the ear harp, assumed by Helmholtz and others, as an impossibility and maintains that the ear is an apparatus to measure the intervals between shocks, distinguishing the higher tones by their shorter, and the lower tones by their longer, intervals. He does not believe that a properly constructed soundboard has any transverse vibrations which affect the tone, as demonstrated by the successful experiments of Mathushek and Moser, whose double soundboards were glued together so that the grain of the one crossed the grain of the other at right angles. This method of construction makes any transverse vibration impossible, and instruments containing such boards are not inferior in volume and quality of tone to any other.
Hansing thus proves that the soundboard does not give forth sounds, but that it only augments and transmits the sound originating with the string, thru a tremor, which is the effect of the motion producing the sound ; namely the percussion of the string by the hammer. This important discovery will assist materially in the further search for soundboard improvements, but even Hansing admits that for the present the piano constructor has to rely on empiric experiments for final results.
To mention a few of the most telling experiments made to improve the efficiency of the soundboard we find Jacob Goll, of Vienna, using iron and copper with reasonable success in 1823; but, no doubt the primitive conditions of the metal industries of those days made the use of metal too expensive, as compared to wood. Henri Pape, of Paris, that king of piano empirics, experimented not only with all kinds of wood and metal, but even tried parchment. All these materials transmitted the sound of the strings, except the parchment, which proved totally unfit for use in the treble sections.
During the writer's engagement with the Mathushek factory in 1867-69 exhaustive experiments were made to find the most responsive thickness for a soundboard. With boards from fully one inch in thickness, without ribs, graduated down to boards only three-sixteenths of an inch thick in treble, and with proportionally heavy ribs, numberless tests were made. Curious to relate, all of the pianos had a satisfactory tone, differing, of course, in quality. The thick boards responded with a thick, somewhat stiff, woody quality, the pianos with the thinner boards had a more sympathetic, soulful, but weaker tone. The most satisfactory tone quality was found in the pianos which had the "regulation" soundboard, three-eighths of an inch thick in treble, tapering off to one-fourth of an inch in bass, ribs placed at nearly equal distances apart, except in the last treble octave, where they lay somewhat closer together. These trials and tests proved conclusively that the soundboard does not produce sound by aid of sound waves, but simply transmits and augments the sound produced by the vibration of the string. They further proved that the soundboard is not nearly as much of a factor in tone production as the string, the proper length, thickness and position of which, together with the most advantageous striking point for the hammer, are the all-important factors to be considered in piano construction.
Attempts to increase the volume of tone by using double soundboards, connected by wooden posts or otherwise, the imitation of the violin or cello form, carefully worked out corrugated soundboards, etc., have all been in vain and are discarded for good. Several ingenious devices to sustain the resistance of the soundboard against the downward pressure of the strings are recorded. Among them Mathushek's "equilibre" system, patented in 1879, is perhaps the most scientific, but the result achieved is not in proportion to the increased cost. Mathushek surmised, what Hansing established as a scientific fact, that the soundboard is not affected by so-called sound waves, and when he discarded his equilibre system because of its high cost, he returned to the thick soundboard without ribs. In 1891 he patented his duplex soundboard, which is a combination of two boards, cross-banded and glued together. The boards are made thickest at the center where the bridge rests, in order to withstand the pressure of the strings.
On October 2, 1900, Richard W. Gertz obtained a patent for a tension resonator for pianos, the purport of which is to regulate the pressure in the arch of the soundboard against the strings and to assist the vibratory efficiency of the entire soundboard, thereby increasing the intensity of the tone produced by the striking of the hammer against the string.
Another function of this resonator is to restore the original arched form of the soundboard when, through age or atmospheric influences, the same has given away to the pressure of the strings. The tension rods with the conical shaped head, inserted into the rim, draw together the entire rim upon which the soundboard is fastened, and force the latter back to its original arched form, reinstating and enlivening the vibratory action of the entire board.
Radiating from the center of the piano to all parts of the rim the tension rods can be screwed up, either simultaneously to bring pressure upon the entire board, or individually if any part of the soundboard should show a pronounced flatness. They are furthermore of great value in maintaining the correct form and shape of the rim. This invention has been applied to all the grand pianos made by Mason & Hamlin since the granting of the patent.
Experience so far has shown that the best material for soundboards is the wood of the fir tree, growing in the mountain regions of Southern Europe and North America.
Whether or not the development of the steel industry will furnish the piano maker eventually with rolled sheets for soundboards, made of proper vibratory metal, and in tapered form, is speculative. It is not improbable, however, that the piano of the future may have a metal soundboard. We do know that the sound in the piano originates with the steel string, and that it is only transmitted by the soundboard, materially assisted by proper construction of the wooden frame of the piano. We also know that the iron frame has no deleterious influence upon the tone quality, and since all piano constructors are still seeking for a clear, bell-like, singing quality of tone, may not the solution be found in a soundboard of steel, so constructed as to successfully withstand the pressure of the strings, and to assist the steel strings in tone production?
Evidently the soundboard is the only part of the modern piano which calls upon the inventor for further investigation, on scientific lines, until the laws are found upon which to build a piano, not necessarily with a louder, but with a more soulful tone, such as the old clavichord possessed in limited quantity.
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