"Ga i air?"
Translation:May I have a word?
"Au" is different to "Ai" in the north since up here we pronounce "u" like you do in french whereas in the south they pronounce it like an "ee" sound. "Ae" can either be "ah-eh" as in "aer" or it can form a dipthong and be pronounced "ey" as in words like "Aeddfed" (Mature) and "Gaeaf" (Winter - pronounced "Gey-av". To here the differences go to "Forvo.com" and use the words "Gair", "Aer", and "Aeddfed". Try the word "Pethau" too though this will be different depending on if they have pronounced it formally with the full "Au" ending (which again differs depending on North/South) or if they pronounce it colloquially which typically means they don't pronounce the "u" at all.
Perhaps to summarise this a bit more clearly (with IPA in square brackets):
ai, au are both [ai], like English "eye".
ae is [ai] "eye" too in a final syllable. In a non-final syllable it's [ei], like English letter "A".
ai [ai], English "eye"
au [aɨ], similar to English "eye" but the tongue finishes futher back in the mouth. It's a combination of Welsh a and northern Welsh u.
ae in a final syllable [aːɨ], just like au but the a held longer. In a non-final syllable it's [eɨ], so like English letter "A" but the tongue finishes futher back in the mouth. It's a combo of Welsh e and northern Welsh u.
As you can see, the northern pronunciations are a bit involved if you're a beginner and you can probably get away with pronouncing them all "eye" to start with and still be understood. To a southerner, Cai [boy's name], cau "close", cae "field" all sound the same. To a northerner they're all different.
The other point @EllisVaughan refers to is that in colloquial or informal Welsh, ai, au, ae in a final syllable are often pronounced e [ɛ] in most of Wales, except in the north-west, where they're pronounced a [a]. So informally, people will often pronounce cadair "chair", gorau "best", gwahaniaeth "difference" as cader, gore, gwahanieth except in the north-west, where they're cadar, gora, gwahaniath.
Something else to be aware of too is that in the south-west, ae in a monosyllabic word is often pronounced â [aː] in the colloquial language, so llaeth "milk" is llâth, cae "field" > câ, aeth "went" > âth etc. In fact, that's how we get the word mas "out", from the word maes "field" pronounced colloquially.