176 Sound emitted by Wires of Circular Section. 



of VD/i; the frequency of the note emitted is that of eddy 

 formation. It was unfortunately impossible to obtain higher 

 water speeds in the existing channel, but this was not con- 

 sidered vital to the demonstration, since it was possible to 

 obtain sufficiently low values of YDjv in air to check the 

 agreement of the water and jiir experiments over a consi- 

 derable range of the above argument. 



It will further be seen that at values of VD/V above 500 

 the value of nT)/Y is constant, and the frequency of the 

 emitted note is directly proportional to velocity, and in- 

 versely proportional to diameter of wire. The curve obtained 

 at low values of YDJv indicates departure from this strict 

 proportionality, and is a feature common to all fluid flow 

 problems at low speeds. At a value of YD/v slightly lower 

 than that of the last point on the curve, the flow becomes 

 steady and eddies are no longer formed. For any given 

 wire there is accordingly a limiting velocity, given roughly 

 by VD/y=100, below which no sound will be emitted. 



- Experiments on Wires of Circular Section. 





Water Experiments. 





Diameter 



of Wire. 



(ins.) 



T7- i -4- Periodic mTk 

 Velocity. Time «D 



ms '/ sec - (sees.). V 



YD 



V 



0-25 



075 2-65 0-126 



110 



025 



1-25 1-31 0-154 



180 



0-4 



1-20 2-00 0-167 



270 



0-5 0-74 4-13 0-164 210 



05 1-23 # 2-38 0-172 350 



Air Experiments. 



Diameter 



of Wire. 



(ins.). 



Velocity. 



ft./sec. 



17 wD 



Frequency. . 



VD 



V 



o-oio 



24-5 



4000 



0-136 



125 



0015 



22-6 



3000 



0-166 



180 



0015 



29-3 



4000 



0-170 



230 



0-030 



32-4 



2400 



0-186 



510 



0-030 



40-5 



3000 



0-185 



640 



0-048 



41-6 



2000 



0192 



1050 



048 



54-2 



2500 



0-185 



1360 



o-iio 



48-9 



1000 



0-187 



2820 



0110 



60-3 



1200 



0-182 



3460 







r Air 



0-000159 







Value of v ■ 



i Water... 



0-0000122 





