HANDBOOK OF ACOUSTICS - online book

A complete view of Acoustical Science & its bearings on music, for musicians & music students.

Home | Just The Tune | Order | Contact




94                      HAND-BOOK OF ACOUSTICS.
With regard to the string, the more flexible it is, the more readily will it break up into vibratory segments, and therefore the greater will be the number of partials in its tones. Thick stout strings, such as are used for the lower notes of the harp, cannot from their rigidity break up into many segments, and therefore the fundamental will be louder than the other partials. On the other hand, thin strings of catgut, such as first violin strings, readily vibrate in many segments, so that their tones contain many partials. Still more is this the case with a long fine metallic wire, in which it is possible to hear some fifteen or twenty partials, the fundamental being very faint or even inaudible. The tinkling metallic quality of tone from such a wire, is due to the prominence of the high partials above the seventh or eighth, which lie at the distance of a tone, or less than a tone, apart. Again, the steel wires which give the highest notes in the pianoforte, being already so short, cannot readily break up into vibrating segments, and hence the highest tones of this instrument are nearly simple.
As we have seen, the three chief methods of setting strings in vibration are: by a blow from a hammer, by bowing, and by plucking. In the first method (employed, for example, in the pianoforte) the quality of the tone is largely affected by the nature of the hammer. If it is very hard, sharp, and pointed, the part of the string which is struck by it will be affected, and the hammer will have rebounded, before the effect of the blow has time to travel along the length of the wire. Thus small ventral segments will be formed, and prominent upper partials will be produced, the lower ones being feeble or absent. On the other hand, if a very soft, rounded hammer be used, the blow being much less sudden, the movement of the wire will have time to spread, and a powerful fundamental may be expected. On the pianoforte, both extremes are avoided, by covering the wooden hammers with felt, so that when they strike the wire, the rebound is not absolutely instantaneous ; nevertheless the time during which the hammer and wire are in contact is extremely short. Similarly, in plucking; a soft, rounded instrument, such as the finger tip, gives a stronger fundamental and fewer high partials, than the harder and sharper quill, that used to be employed in the harpsichord.
The quality of the tone, given forth by a stretched string, depends largely upon the point at which it is struck, bowed, or plucked. We have already seen, that the point in question cannot be a node; it is more likely to become the middle of a ventral segment. All the partials, therefore, that require a node at that