At lower (audio) frequency, lower output impedance of generator and higher input impedance of receiver is prefferable.
This program calculates by following circuit model to get insetion loss.
+-Rs-o---+---R---+---o-+ | | | | G C/2 C/2 Rr | | | | +----o---+-------+---o-+ <--- cable ---> G = microphone, Rs = output impedance of microphone (Ohm) R = resistance of cable (Ohm), C = capacitance of cable (F) Rr = input impedance of amplifier (Ohm)