[lang] 



HIGH FREQUENCY VIBRATIONS, ETC. 



171 



and air remain constant at the high frequencies and, as already 

 indicated, are the same as in the ordinary frequency range. 



10 



20 30 40 so 



WAVELENGTH /N METAL IN CMS. 



60 



Damping 



On the-question as to whether the damping by "soHd viscosity" 

 afifects the velocity in these metal rods, the evidence here is that up 

 to a frequency of 50,000 vibrations per second the damping is not 

 sufficient to afïect the velocity of the natural period appreciably. 

 Cady^ points out that the true velocity ic) is given by the relation 



1/ ^•'~ 4 _ 



/Ê 27r 



where Co is the velocity given by ]/ - , iv = t" , 



X being the wave length, and Q a factor depending on the "solid 

 viscosity." There is no value for Q yet quoted. 



In attempting to obtain the dust figures for these bars ranging 

 from 200 cms. to 5 cms. in length a matter arose which shpuld be 



^Theory of Logitudinal Vibrations of Viscous Rods, Phys. Rev., Jan., 1922. 



