ELEMENTS 



53 



From equations 4.10, 4.11, 4.12 and 4.13 the pressure is 



4.14 



From the definition of acoustic capacitance, equation 4.14, the acoustic 

 capacitance of a volume isj 



V 

 Ca = — 4.15 



Then equation 4.14 may be written, 



P 



X_ 

 Ca 



4.16 



Equation 4.16 states that the volume displacement in an acoustic capaci- 

 tance is proportional to the pressure and the acoustic capacitance. 



CAPACITANCE 

 ELECTRICAL 



COMPLIANCE 

 MECHANICAL 



CAPACITANCE 

 ACOUSTICAL 



Fig. 4.1. Graphical representation of the three basic elements in electrical, mechanical and 



acoustical systems. 



4.5. Representation of Electrical, Mechanical and Acoustical Elements. 

 — Electrical, mechanical and acoustical elements have been defined in the 

 preceding sections. Figure 4.1 illustrates schematically the three elements 

 in each of the three systems. 



Mechanical resistance is represented by sliding friction which causes 

 dissipation, x^coustic resistance is represented bv narrow slits which 

 cause dissipation due to viscosity when fluid is forced through the slits. 

 These elements are analogous to resistance in the electrical system. 



Inertia in the mechanical system is represented by a mass. Inertance 



