The reason the ABR does not identify small tumors can be explained by the fact that ABRs rely on latency changes of peak V. Peak V is primarily influenced by high-frequency fibers, and tumors will be missed if those fibers aren't affected. Although the click stimulates a wide frequency region on the cochlea, phase cancellation of the lower-frequency responses occurs as a result of time delays along the basilar membrane. If a tumor is small, it is possible those fibers won't be sufficiently affected to be detected by the traditional ABR measure.