There are many dialects in Japan even it is a small island country.
Japan is consisted from 47 prefectures and it is largely divided up 8 areas; Hokkaido, Tohoku, Kanto, Chubu, Kinki, Shikoku, Cyugoku, Kyusyu.
They have their own dialog and intonation and it is sometimes hard to listen or understand what they are saying for people from other area.
For example, Tohoku district has very unique dialog and intonation. It sounds like French. Kyusyu district has also very unique and sometimes we cannot understand what they are saying at all.
In case of 3.11 (Earthquake), doctors of other district went help but could not have communication smoothly with patients because of the dialog.