Sounding board

The sounding board is the part of the Musical instrument to cords which receives the vibration directly to be amplified, of the cord through the rest.

Principle

Indeed, the surface of the cords of the string instruments being very weak, the vibration of a cord produces only one its very weak. By transmitting the vibration of the cord to a large surface, its product is definitely more important, at the price of a faster damping of the vibration.

It is about a sheet of wood very thin of one with (a few millimetres) and extended, generally made in spruce. In certain traditional instruments, it is a skin under tension which plays this part. Tests were carried out with other matters, such as a sheet, but with mitigated successes.

Transmission of vibration of cord with table is ensured by angulation of cord which is done on the level of a rest (the edge of the rest is slightly far away from the sounding board compared to the trajectory that the cord would have if it were simply tended between its two fasteners), the tension of the cords making the remainder. This provision is easy to see on a violin, but difficult on a piano.

When it sounding board is broken down, the cord does not form any more an angle and does not transmit almost any more vibrations to the table, from where a loss of sound.

Provision and manufacture

As the sounding board is fixed on its circumference, the rest must be placed further possible from the edges in order to acting on a part which vibrates easily.

The sounding board, so fine compared to its wide, must be rigidified (or “put in tension”) by a stopping, i.e. wood bars stuck under the table (in the case of the Piano, one speaks rather about coasts, the stopping being the structure of the instrument). This stopping, seldom visible without disassembling (Violin) or without passing under the instrument (piano), constitutes an basic element in the sonority of the instrument. Generally, it was a jealously kept secrecy. To note that the pressure of the cords rigidifies also the table, and that a balance settles then between the force of the bars of dimensioned, pressure of the cords of the other. This allows various approaches when the acoustic properties of the table.

The sounding board of the complex piano being of form, it is often necessary to block the vibrations in an angle. This is carried out by means of a handkerchief , bars of rigid wood which isolates a triangle in a corner from the sounding board.

Openings

In many instruments, the sounding board is bored openings which make it possible the case not to be not a closed space, and thus with the air which it contains to be in relation to the surrounding air. These openings bear various names: rosette (of round form) for the Lute, the Guitar, the Harpsichord, hearing (in form of F of partition) for the Violin S, viola S, Violoncello S, Double bass S, and also for the Viol S (in form of C ). The influence on acoustics of the instrument is probable but badly known.

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