532 On the Effects of Vibration in Iron Rods. 



of the sonometer with the calculated values. The following 

 table shows (a) the calculated frequencies of the fundamental 

 and first overtones ; (b) the frequencies detected by listening 

 directlv to the bar ; (c) the frequencies detected in the tele- 

 phones when the coil was placed near the rod. 





Calculated 

 frequency. 



Observations In- 

 direct listening. 



Observations with 

 search-coil near rod. 



Fundamental ... 



20-8 



(Below 



audibility.) 







1st overtone ... 



2nd „ 



3rd 



130 

 365 

 715 



Freqn 



ericy 140 



detected. 

 366 do. 



745 do. 



Uncertain. 



Frequency 366 



detected. 

 „ 745 do. 



4th „ 



1180 



,, 



1180 do. 



Uncertain. 



5th „ 



1770 



Not heard. 



Not heard. 



To obviate the damping effects due co the cable, this was 

 disconnected from the bar during the foregoing observations. 



It will be observed that though the first and fourth over- 

 tones were distinguished by direct listening, they could not 

 be distinguished with certainty in the receivers. They may 

 have been present, but were masked by the more prominent 

 second and third overtones which could not be suppressed. 



As the coil was rotated between the positions C, P, and R. 

 variations of quality were observed, and the concentric com- 

 ponent was in general less intense than the parallel or radial 

 components. 



Conclusions. 



The phenomena observed indicate that complex magnetic 

 changes are produced in an iron bar by its own vibrations. 



Though the mode of vibration of the bar determines the 

 period of its vibration and therefore the period of the magnetic 

 oscillations v\ Inch result therefrom, no very simple and definite 

 relation exists between the mode of vibration and the structure 

 of the resulting magnetic field. (Longitudinal vibration 

 seemed, however, to be associated with a marked oscillation 

 in the longitudinal magnetization.) 



It may be noticed as a point of practical importance that 

 such " magneto- mechanical" effects may lead to disturbances 

 in sensitive electrical circuits which pass near moving steel 

 machinery unless those circuits are shielded or rendered non- 

 inductive. 



