Matching  --  Arranging for the impedances presented by a load to be equal to the internal impedance of the generator; this is essential to avoid loss of power. In mikes, the loss results in poorer signal-to-noise ratio. Matching is done by means of a transformer. Where mike impedance is strongly capacitative; e.g., in electrostatic types the output voltage is fed to the grid of a valve and controls the current in an external circuit.