I have a coursebook by Doyle and Gussmann in which they introduce Munster dialect wherever possible and they give the following examples: ghnáth /ɣna:/ or ghrá /ɣra:/ Ghleanna /jlanə/ or ghrian /jr'iən/ and also: Ghall /ɣaul/ vs gheall /jaul/ Now I am really confused. After reading the paragraph in my coursebook I thought that maybe gh is pronounced as /j/ when it is followed by e or i letter or sound. But as it is in the ghloine example, the speaker pronounces /ɣ/ even when it is followed by i sound. There is also this source (I know it is another word than the one considered in this Comments section): http://www.fuaimeanna.ie/en/Recordings.aspx?Ortho=gheall which tells me that according to Celticist phonemic transcription it's /ɣ'/ - different than /ɣ/ and /j/.
So please explain if you can, how is that? Is it really dialectal difference?
In Irish, the broad gh is pronounced /ɣ/ (or is silent after a long vowel), and the slender gh is pronounced /j/. Whether a given gh is broad or slender depends upon the nearest vowel in its syllable: if it’s e, é, i, or í, then it’s slender; otherwise, it’s broad. (Note that the digraph ae is considered to be a single broad vowel.) That is, it’s not the vowel sound that’s the determining factor, but the vowel letter (ignoring the e of ae). Thus, the gh in ghnáth, ghrá, Ghall, or ghloine is broad, since the nearest vowel is either á, a, or o, and is therefore pronounced /ɣ/; and the gh in Ghleanna, ghrian, or gheall is slender, since the nearest vowel is either e or i, and is therefore pronounced /j/.
I’m not familiar with Celticist notation, but judging from the transcriptions at that fuaimeanna.ie link, it looks as if Celticist /ɣʹ/ = IPA /j/, which makes sense for gheall.
There can be a dialectal difference in how the vowel itself is pronounced in a word like Ghall — /ɣɔul̪ˠ/ in Munster, /ɣɑːl̪ˠ/ in Connacht, and /ɣal̪ˠ/ in Ulster.