Piano string excitation IV: The question of missing modes
作者:
Donald E. Hall,
Peter Clark,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1987)
卷期:
Volume 82,
issue 6
页码: 1913-1918
ISSN:0001-4966
年代: 1987
DOI:10.1121/1.395686
出版商: Acoustical Society of America
关键词: STRINGS;MUSICAL INSTRUMENTS;OSCILLATION MODES
数据来源: AIP
摘要:
It is usually said that a force applied to an extended vibratory system is incapable of exciting any normal mode that has a node at that point. Thus piano hammers positioned to strike the strings at certain fractions of their length should produce spectra with ‘‘missing modes.’’ However, this has been disputed by some observers, and it is sometimes suggested that more careful theoretical treatments would justify a restoration of those modes. Spectra of string motion have been measured as a function of hammer position by moving a piano action frame in small increments along the bed of the case. It is found that there are indeed sharp minima in mode amplitudes (on the order of 20 to 30 dB down) as the striking point passes within a few millimeters of the nodal positions. Possible limitations on the theoretical arguments are discussed, and it is concluded that the small residual strengths in the nearly missing modes can be well accounted for by finite soundboard admittance.
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