For example, this is how the phrase "ich bin daheim gewesen" (I was at home) sounds in the different areas of the Black Forest: it is pronounced i bin dahaaim gwää in Gernsbach, i ben daheim gwä in Pforzheim and i be dahaem gwää in Wildbad. However, south of a line from Bühl to Nagold in the western part of the central Black Forest, it sounds completely different: i bin dahaim gsi (or even gsii). It is i bi dahai gsi in the South in Göhrwihl and i bin dahó gsi on the eastern border of the central Black Forest in Schramberg. In neighbouring Tennenbronn, you will hear i bin dahóam gsi - and, even more markedly, in Baiersbronn, they say i bãe dahãem gsãe.
Note on the phonetics: I am attempting to reproduce the exact articulations in the dialect examples using the normal alphabet. Only for the 'open' o-sound, which lies between a and o, I am writing ó. The tilde indicates that the vowel indicated by it is pronounced nasally. Where vowels are written as double vowels, I am indicating that they are pronounced 'long' (like o in the High German word "Brot"). We have the industrious research carried out by a whole series of dialectologists - some of whom were working as long as a hundred years ago - to thank for what we know about these and many other dialect boundaries. These scholars conducted first written, and then later also oral surveys among dialect speakers.