A Formula for the Transfer Function of Electro-Acoustical Transducers and Its Relations to Electrical Equivalent Circuits

A frame formula (8)

A _w ¹ = M1/w K

is derived for the standardized transfer functions of electroacoustic transducers. This applies to transmitters and receivers when corresponding values K _e and K _s which differ by the reciprocity parameter I are inserted for the mechanoacoustic conversion constant K.

If the feedback of reversible transducers of high efficiency cannot be neglected, the quadripole equations (I) and (II) must be taken into account by including the blocked impedance

w _b = M ²/Z _a+Z _v=0

for receivers or the motional impedance Z _mot = M ²/w for transmitters. Extended formulae are in this way arrived at for the transducer transfer functions under different operating conditions. The result agrees with that obtained from electrical equivalent circuits if their quadripole transfer coefficient A _v is multiplied by the electroacoustic transfer coefficient A _ea as a conversion factor.

In conclusion the validity ranges of formulae and equivalent circuits are discussed and the essential differences between a real transducer and its analogous electrical equivalent circuit diagram are defined.