Audio Engineering

684 Chapter 23

The beauty of the analogue method of analysis is that it is possible, by using various
transformation equations, to refer the acoustic and electrical parameters to the mechanical
side or, conversely, the mechanical and acoustic parameters to the electrical side, etc. For
the purpose of this analysis the electrical and acoustical parameters are referred to the
mechanical side. The diaphragm can be thought of as an acoustic/mechanical transducer,
that is, a device for transforming acoustic energy to mechanical energy, and vice versa.
Under these circumstances it will also act as an impedance transformer, that is, it will
convert acoustic inertance into mechanical mass and acoustic compliance into mechanical
compliance and acoustic resistance into mechanical resistance. The equivalent
mechanical values of the acoustical quantities may be obtained from the following
relationships:

Mechanical Acoustic

Force pressure Area

Newtons

Veloci



Fpsdm  

tty

Volume velocity

Area



(23.18)

u

Sd



U

(23.19)

Displacement

Volume displacement

Area



x

x

Sd

v (23.20)

Resistance Acoustical resistance Area squared

ma



RRSd   ^2 (23.21)

Mass   Inertance Area squared

mMSd   ^2 (23.22)

Compliance

Acoustical capacitance

Area squared

m

a



C 

C

Sd^2

(23.23)