CORRECTIVE NETWORKS 



63 



the velocity transmission will increase with frequency as shown by the 

 characteristic of Fig. 4.5D. 



The acoustical system, Fig. 4.5C, consists of a pipe with a side branch 

 forming an inertance. At low frequencies the reactance of the inertance 

 is small compared to the impedance of the pipe and the sound is shunted 

 out through the hole. At high frequencies the reactance of the inertance 

 is high compared to the impedance of the pipe and the sound wave flows 



M 



ELECTRICAL 



fm] J 



B 



FREQUENCY 



P 



RESPONSE CHARACTERISTICS 



Fig. 4.5. A line shunted by the following: A an inductance. E a capacitance. / an induc- 

 tance and a capacitance in series. M. an inductance and a capacitance in parallel. The 

 mechanical equivalents are shown in B, F, J and A''. The acoustical equivalents are shown 

 in C, G, K and 0. The transmission-frequency characteristics are shown in D, H, L and P. 



down the pipe the same as it would in the absence of a branch. Since 

 the impedance of an inertance is proportional to the frequency, the volume 

 current transmission will increase with frequency as shown by the charac- 

 teristic of Fig. 4.5D. 



C. Capacitance in Shunt with a Line and the Mechanical and Acoustical 

 Equivalents. — In Fig. \.SK a capacitance is shunted across a line. The 

 reactance of a capacitance is inversely proportional to the frequency. 



