﻿THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] /^ 



APRIL 1915. 



XLVIII. JSoliah Tones. 

 By Lord Rayleigh, O.M., F.R.S* 



IN what has long been known as the iEolian Harp, a 

 stretched string, such as a pianoforte wire or a violin 

 string, is caused to vibrate in one of its possible modes by 

 the impact of wind ; and it was usually supposed that the 

 action was analogous to that of a violin bow, so that the 

 vibrations were executed in the plane containing the direc- 

 tion of the wind. A closer examination showed, however, 

 that this opinion was erroneous and that in fact the vibra- 

 tions are transverse to the windf . It is not essential to the 

 production of sound that the string should take part in 

 the vibration, and the general phenomenon, exemplified in 

 the whistling of wind among trees, has been investigated by 

 StrouhalJ under the name of Reibung stone. 



In Strouhal's experiments a vertical wire or rod attached 

 to a suitable frame was caused to revolve with uniform 

 velocity about a parallel axis. The pitch of the seolian tone 

 generated by the relative motion of the wire and of the air 

 was found to be independent of the length and of the tension 

 of the wire, but to vary with the diameter (D) and with the 

 speed (V) of the motion. Within certain limits the relation 



* Communicated by the Author. 



f Phil. Mag-, vol. vii. p. 149 (1879) ; Scientific Papers, vol. i. 

 p. 413. 



% Wied. Ann. vol. v. p. 21 G (1878). 



Phil. Mag. S. 6. Vol. 29. No. 172. April 1915. 2 V 



