Fundamental vibration

When a string is fixed at both ends, many normal vibrations occur, but the lowest frequency vibration has a wavelength equal to half the length of the string. This vibration is called the fundamental vibration of the string. The normal vibration of a string also has frequencies that are integer multiples of the fundamental vibration, such as twice, three times, etc., and wavelengths that are integer fractions of the wavelength of the fundamental vibration, such as half, one-third, etc. These vibrations are called harmonic vibrations. Fundamental and harmonic vibrations occur not only in the lateral vibration of a string, but also in the normal vibration of the air in a tube or the longitudinal vibration of a rod.

[Yoshiro Kainuma]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

両端を固定した弦の振動には、多数の基準振動が生ずるが、振動数最低の振動においては、波長は弦の長さの半分に等しい。この振動を弦の基本振動とよぶ。弦の基準振動には、この基本振動の振動数の2倍、3倍、……など整数倍の振動数をもち、波長が基本振動の波長の2分の1、3分の1、……など整数分の1に等しい振動も生ずる。これらの振動は倍振動とよばれる。弦の横振動に限らず、管の中の空気や棒の縦振動の基準振動においても、基本振動、倍振動が生ずる。

［飼沼芳郎］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例