| Share page | Visit Us On FB |
|
116 ACTION OF SOUND-BOARD. [V. § 56. |
||
|
pianoforte notes varies greatly in different parts of the scale. In the lower and middle region it is full and rich, the first six partial-tones being audibly present, though, 4, 5, 6 are much weaker than 1, 2, 3. Towards the upper part of the instrument the higher partial-tones disappear, until in the uppermost Octave the notes are approximately simple-tones, which accounts for their tame and uninteresting character. The pianoforte shares with all instruments of fixed sounds certain serious defects which will be discussed in detail in a subsequent chapter.
When a vibrating wire is passing through its undisturbed position, its tension is necessarily somewhat less than at any other moment, since, in order to assume the curved segmental form, it must be a little elongated, which involves a corresponding increase of tension. Hence the two pegs by which the ends of a wire are attached to the sound-board are submitted to an additional strain twice during each complete segmental vibration. The sound-board, being purposely constructed of the most elastic wood, yields to the rhythmic impulses acting upon it, and is thrown into segmental vibrations like those of the wire.
These vibrations are communicated to the air in contact with the sound-board, and then transmitted further in the ordinary way. The amount of surface |
||