Cochlea a protein motor called prestin on their outer membranes; it generates additional movement that couples back to the fluid–membrane wave. This "active amplifier" is essential in the ear's ability to amplify weak sounds. The active amplifier also leads to the phenomenon of soundwave vibrations being emitted from the cochlea back into the ear canal through the middle ear (otoacoustic emissions). Otoacoustic emissions are due to a wave exiting the cochlea via the oval window, and propagating back through the middle ear to the eardrum, and out the ear canal, where it can be picked up by a microphone. Otoacoustic emissions
Stirrup jar termed "unpainted" although in fact the viewer sees the first coat. It is not the color unpainted fired terra cotta would have; that would be variegated most likely ranging from red to black depending on the firing parameters and content of the clay. For example, Black Glazed Ware features a single coat of black glaze. Red-figure vases are washed with a black slip on which red figures are painted; black-figure vases, a red wash with black figures. Stirrup jars do not bear human figures; nevertheless, some are quite ornamental, with most of the painting surfaces filled with motifs. The stirrup