**4. Stria vascularis**

#### **4.1. Direct current (DC) voltage source in the cochlea**

A fundamental role in the cochlear amplifier, besides the OHCs, is played by the stria vas‐ cularis, which produces a source of DC voltage between endolymph and perilymph. This potential difference, resulting from difference in ion concentrations in endolymph and peri‐ lymph, is sustained by metabolic processes occurring in the cochlea. This source of a DC voltage stores energy in the form of an electrical (potential) energy. In fact, the cochlear ampli‐ fier draws energy from the stria vascularis battery to amplify power of an incoming acoustic wave. The stria vascularis battery will play a key role in the generation of electrical signals and currents (both direct and alternating) flowing in the cochlear amplifier. In the circuit model of physical phenomena in the cochlea, the stria vascularis is represented by a (DC) voltage source, see the upper left part of **Figure 1**.
