Figure 1.

Diagram showing DP generation and propagation and measurement of the backward delay. (A) Two tones f1 and f2 enter the cochlea through the external and middle ear to result in traveling waves f1 and f2, which generate DPs at their overlapping location (DP site). DP was measured at the BM, at the stapes, and in the ear canal. (B) When a DP wave is generated at the apical side of the measured BM location, the propagation direction of the wave can be determined by the phase difference from the BM to stapes. The wave should propagate from a location with a phase lead, to a location with a phase lag. RW is the round window; OW, the oval window.