ONE DEGREE OF FREEDOM 59 



said to have a magnitude of one abohm when a voltage of one abvolt pro- 

 duces a current of one abampere. 



Mechanical impedance is the complex quotient ot the force by the linear 

 velocity. The unit is the mechanical ohm. 



Mechanical resistance is the real component of the mechanical imped- 

 ance. The unit is the mechanical ohm. 



Mechanical reactance is the imaginary component of the mechanical 

 impedance. The unit is the mechanical ohm. 



Mechanical ohm. A mechanical resistance, reactance or impedance is 

 said to have a magnitude of one mechanical ohm when a force of one dyne 

 produces a velocity of one centimeter per second. 



Acoustical impedance is the complex quotient of the pressure by the 

 volume current. The unit is the acoustical ohm. 



Acoustical resistance is the real component of the acoustical resistance 

 impedance. The unit is the acoustical ohm. 



Acoustical reactance is the imaginary component of the acoustical im- 

 pedance. The unit is the acoustical ohm. 



Acoustical ohm. An acoustical resistance, reactance, or impedance is 

 said to have a magnitude of one acoustical ohm when a pressure of one 

 dyne per square centimeter produces a volume current of one cubic cen- 

 timeter per second. 



E. Resonant Frequency . — For a certain value of L and Cb, m and Cm-, 

 and M and Ca there will be a certain frequency at which the imaginary 

 component of the impedance is zero. This frequency is called the resonant 

 frequency. At this frequency the ratio of the current to the applied voltage 

 or the ratio of the velocity to the applied force or the ratio of the volume 

 current to the applied pressure is a maximum. At the resonant frequency 

 the current and voltage, the velocity and force, and the pressure and vol- 

 ume current are in phase. 



The resonant frequency /r in the three systems is, 

 Electrical 



fr = ^ 4.45 



Mechanical 



Acoustical 



fr = 7= 4.46 



fr 7= 4.47 



2tVmCa 



