Thanks; now I have found
this page that says it is [ti:s'@x] where symbols have the following meaning (according to their
phonology page):
i: = long i (English ee)
@ = schwa (English a in above)
ti: with aspirated initial t like in English, and a velar offglide t@i:
s' = English sh, or rather an alveopalatal fricative like Polish si
x = ch in loch
So with English sounds it would be something like Tee-shoch (ch in loch) or Tee-shah.
Irish is even worse than English as for writing!
-- Olivier