Can someone please explain to me why is "Soitheach" pronounced something like "saah-yuhkh"? If I see this word for the first time, how am I to eliminate the vowels that do not contribute to the pronunciation?
As I understand it, you don't eliminate vowels like we do in English. The vowels work/flow together. In your phonetics above, the s is the s, the 'aah' is the o, the 'y' is the i , the u is the e and the sound hkh is the a blending in to the ch.