Dr. Rustin Berlow locates the auditory cortex using the measured distance between tragus to tragus.

Locating the auditory cortex is relatively straightforward, depending on the method that you are using. The preauricular point is right here (points in front of the ear). Since we know that the distance from tragus to tragus is 36(cm), we can take 10% of that, which is 3.6(cm). 10% above the preauricular point is T3. If we were going to identify P3 and take the location halfway between there, we would be more above the ear as opposed to the preauricular point.