Soundboard

“ In looking at a harp we recognise at once the varied functions of its structure. The resonant instrument is the soundboard, forming with its body the angle next the player. The opposite angle is the pillar. Both support the neck, a curved bracket between which and the soundboard the strings are stretched. ”

“ In this action he worked the hammers from the front ends of the keys, and thus saved a foot in the length of the case, which he strengthened up to due resistance of the tension without iron barring. He lowered the soundboard, glueing the belly-bars to the upper instead of the under surface, and attached the belly-bridge by a series of soundposts. ”

“ In front, immediately over the keys, is the wrestplank, with the tuning-pins inserted, round which are wound the nearer ends of the strings—in this instrument two to each note—the further ends being attached to hitchpins, driven into the soundboard itself, and following the angle of the bent side of the case to the narrow end, where the longest strings are stretched. There is a straight bridge along the edge of the wrestplank and a curved bridge upon the soundboard. ”

“ As it lay in the case under glass, the measurements as near as I could take them were,—length of arms or uprights 15 inches, the crossbar fixing three inches below the tips of these, and extending 11⁄2in. beyond, between the arms the width at the crossbar 71⁄2in. increasing in the curves to 81⁄2in., the shell with soundboard I reckon as about 7 by 31⁄2in., thus the whole length appears to be 22 inches. The general look of it gives the idea of graceful slimness, the wood is sycamore, and the construction of the lyre so simple that it might have been home-made. ”

“ The sounding-board—a thin, clear sheet of spruce under the strings—is the piano's soul, wanting which, it were a dead thing. Almost every resonant substance in nature has been tried for sounding-boards, but nothing has been found equal to spruce. Countless experiments have been made with a view to ascertain precisely the best way of shaping, arranging, and fixing the sounding-board, the best thickness, the best number and direction of the supporting ribs; and every great maker is happy in the conviction that he is a little better in sounding-boards than any of his rivals. ”

“ The cure for the trouble is brought about by the introduction of materials such as carpets, tapestries, and the like, which act as absorbers of sound and reduce the time of reverberation.
When music is played in an auditorium with a prolonged reverberation, the tones following one another blend and produce the same effect as that of a piano when played with the loud pedal in use. A reverberation is more advantageous for music than for speech, since the prolongation and blending of the musical tones is desired, but the mixing of the words in a speech is a distinct disadvantage. ”

“ The size of the flame and its position in the tube will give a certain note which will be the same note as the air would emit if in a pipe, for the vibrations give the sound.
Sir Charles Wheatstone has shown by experiment how sound can be transmitted by placing a rod on a musical-box, and carrying the rod through the ceiling. When a guitar or violin was placed upon the rod, the sounds of the musical-box were distinctly heard in the upper room. A Phantom Band can be made by connecting certain instruments with others being played on under the stage. Every one will then appear to play by itself. ”

“ The special fact appertaining to keyboard instruments is the mechanical action interposed between the player and the instrument itself. The strings, owing to the slender surface they present to the air, are, however powerfully excited, scarcely audible. To make them sufficiently audible, their pulsations have to be communicated to a wider elastic surface, the sound-board, which, by accumulated energy and broader contact with the air, re-enforces the strings' feeble sound. The properties of a string set in periodic vibration are the best known of the phenomena appertaining to acoustics. ”

“ The action is the same on the voice of the speaker. The sounds he utters are complex and as they reach the walls certain components are reinforced and the quality of the sound is changed. This action of resonance may also be caused by the air in a room. Each room has a definite pitch to which it responds, the smaller the volume of the room the higher being the pitch. A large auditorium would respond to the very low pitch of the bass drum. ”

“ The lower end of the rod rests upon a wooden tray, to which the musical vibrations of a body applied to the upper end of the rod are to be transferred. An assistant is above, with a tuning-fork in his hand. He strikes the fork against a pad; it vibrates, but you hear nothing. He now applies the stem of the fork to the end of the rod, and instantly the wooden tray upon the table is rendered musical. The pitch of the sound, moreover, is exactly that of the tuning-fork; the wood has been passive as regards pitch, transmitting the precise vibrations imparted to it without any alteration. ”

“ Experiments and observations show that wires are of practically no12 benefit, and sounding boards can be used only in special cases. Wires stretched in a room scarcely affect the sound, since they present too small a surface to disturb the waves. They have much the same effect on sound waves that a fish line in the water has on water waves. The idea has, perhaps, grown into prominence because of the action of a piano in responding to the notes of a singer. The piano has every advantage over a wire in an auditorium. ”

“ Some neighbouring tribes, however, possess a musical instrument very similar in appearance to the bow, to which they attach a gourd, hollowed and open at the top, which serves as a sound-board. Again, other African tribes have a similar instrument, superior in construction only inasmuch as it contains more than one string, and is provided with a sound-board consisting of a suitable piece of sonorous wood. In short, the more improved we find these contrivances the closer they approach our harp. ”

“ The sound-board is now also slightly curved, forced upward or made convex that it may resist the downward pressure of the bridge that holds the strings slightly elevated from their level, to secure a complete and intimate communion for the transmission of vibrations. It is clear that, if, from any cause, a sound-board should become concave, or loose at any of the sides, serious consequences would ensue. ”

“ With the musical sound given out by these vibrating strings must inevitably be mixed the dull and unmusical sound of the blow that set them vibrating. The trained ear will detect not only the thud of the hammer against the string, but that of the finger against the key, and that of the key itself upon its base. The study of touch and tone upon the piano is the study of the combination and the control of these two elements of sound, the one musical, the other unmusical. ”

“ The acoustic quality of a room may be improved by breaking up the smooth surfaces by curtains or by arrangement of furniture. The echo is then broken up into small waves, none of which may be sufficiently distinct to interfere with the direct voice. Sometimes a sounding-board over the head of a speaker improves the hearing probably by preventing echo from a smooth wall behind him. A large bare floor is undoubtedly bad for acoustics, for when a room is filled by an audience the hearing is much improved. ”

“ The air column in the tube of the French horn, and the sounding-board of the pianoforte develop the vibrations caused by the lips and strings into musical tones pleasing to the ear. The tuning-fork alone can scarcely be heard, while the induced vibrations it sets up through properly adjusted resonance may be audible far away.
The vocal cords alone cannot make music any more than can the lips of the cornet player apart from his instrument. The tone produced by the vibrations alone of the two very small vocal bands must, in the nature of things, be very feeble. ”

“ The f-shaped soundhole has long been used for instruments of all sizes, from the kit to the double-bass, its size being proportionally altered with the scale of the instrument. It is found to produce the maximum of musical vibration, and it is therefore improbable that it will ever be altered in its main features. Uniform as soundholes may appear, they are in fact susceptible of infinite variety in detail, and in their setting in the instrument: and one glance at them is often enough to discover the maker. ”

“ It is not the strings of a harp, or a lute, or a piano, or a violin, that throw the air into sonorous vibrations. It is the large surfaces with which the strings are associated, and the air inclosed by these surfaces. The goodness of such instruments depends almost wholly upon the quality and disposition of their sound-boards.33
Take the violin as an example. It is, or ought to be, formed of wood of the most perfect elasticity. Imperfectly elastic wood expends the motion imparted to it in the friction of its own molecules; the 124motion is converted into heat, instead of sound. ”

“ Chladni’s Tonometer: the Iron Fiddle, Musical Box, and the Kaleidophone
And now let us shorten our rod, so as to bring its vibrations into proper relation to our ears. When it is about four inches long, it emits a low musical sound. When further shortened, the tone is higher; and, by continuing to shorten the rod, the speed of vibration is augmented, until finally the sound becomes painfully acute. These musical vibrations differ only in rapidity from the grosser oscillations which a moment ago appealed to the eye. ”

“ A piano never sounds well on ship-board—the cabins are too small, and the ceilings too low. To the sick and nervous, (and all who are sea-sick become very nervous,) this instrument is peculiarly annoying. Therefore be kind enough to spare them the annoyance. You can practise when the weather is fine, and the invalids are on deck. Pianos have been abolished in many of the finest ships. Such instruments as can be carried on deck, and played in the open air, are, on the contrary, very delightful at sea, when in the hands of good performers—particularly on a moonlight evening. ”

“ If the machine be worn on the shoulders of the officer of the watch he can move as he pleases, and wants no indicator.
The Topophone when used is so constructed, that when a horn is heard, and when the listener is facing the sound, he can hear nothing! When not facing the origin of the sound he can hear the horn very well, but the moment the resonators receive the sound together as they face the source, a very low murmur is heard, or perhaps no sound at all.—Why?
A certain pitch of tone is composed of vibrations or waves of equal length. In all waves there is a hollow and a crest. ”

“ The audience may be large or small, the speaker’s voice high or low, the entertainment a musical number or an address. The best arrangement for good acoustics is then a compromise where the average conditions are satisfied. The solution offered by Professor Sabine is such an average one, and has proved satisfactory in practice.
The problem of architectural acoustics has been attacked experimentally by other workers. Stewart7 proposed a cure for the poor acoustical conditions in the Sibley Auditorium at Cornell University. His experiments confirmed the work of Sabine. ”

“ The only thing essential for the production of a musical sound is that the waves which reach the ear shall be rapid and regular; it is immaterial how these waves are produced. If a toothed wheel is mounted and slowly rotated, and a stiff card is held against the teeth of the wheel, a distinct tap is heard every time the card strikes the wheel. But if the wheel is rotated rapidly, the ear ceases to hear the various taps and recognizes a deep continuous musical tone. The blending of the individual taps, occurring at regular intervals, has produced a sustained musical tone. ”

“ The wires which are tuned to produce the note on the piano corresponding to that of the whistle will vibrate energetically enough to produce a sound themselves. They are the wires to which the impulses are rightly tuned so that each one adds to the motion it has already acquired. We all know how a child sitting in a swing may be made to swing back and forth by giving a succession of little impulses properly timed. The small pushes are superimposed on one another, the result being a single large motion.
FIG. 76.—Analogy between swinging and tuning. ”

“ When he has got a sounding-board ready for a piano, he puts it in the air, rain, snow, sun, or any beastly thing, to warp it, and then he glues crossbars in until it is strong and firm. He’s quite glad when it warps, for you’re about certain nothing more can happen to it. He often cuts into it himself, and glues it again, and so makes it strong. ”

“ In a later investigation6 Sabine showed that the reverberation depended also on the pitch of sound. As a concrete example, the high10 notes of a violin might be less reverberant with a large audience than the lower tones of the bass viol, although both might have the same reverberation in the room with no audience. Again, the voice of a man with notes of low pitch might give satisfactory results in an auditorium while the voice of a woman with higher pitched notes would be unsatisfactory. ”