The problem here for the audio is that it is pronouncing the vowel 'y' as a short vowel, where in fact it should be a long vowel sound. It is saying 'pet-real' where it should be saying 'pet-ree-al'.
This is a problem with the annotation of Welsh where not all long vowels are indicated with the circumflex accent. If you try petrŷal at Ivona.com with Gwyneth it sounds fine.
Thank you very much for the clarification!
If memory serves me well, a phonetic rule I read somewhere said that the standard position for the word's stress in Welsh is the penultimate syllable, which in this case is -ry-, and that a stressed 'y' should sound as 'u bedol', so I was expecting the word to be pronounced 'pet-ree-al'.
That is a better explanation than mine, but opens another point of discussion.
The sound of 'Y' in a word depends on which syllable it is in.
Any syllable but the last one the sound is 'uh' otherwise it is 'ee'
A good example of this is the word for hospital 'Ysbyty' where the first two 'y' have a 'uh' sound and the last one has a 'ee' sound.
Words which are a single syllable usually have the 'Y' sounding as 'ee' for example the word for 'nest' = nyth (nn-ee-th)
There are exceptions the most notable being the definite article where the sound is 'uh'.
Which means my explanation for 'petryal' is not correct and yours is.
However the suggestion that the stressed 'y' is a 'u bedol' is only accurate in the South as in the North, especially Gwynedd the 'u bedol' is a different more nasal sound.
All this is explained on the excellent Youtube channel 'Welsh Plus'
Extra thanks for the in-depth explanation.
The rule of thumb I mentioned is clearly wrong, because in 'ysbyty' the stress falls on the -by- syllable, which though sounds as 'uh' (or schwa, ə), not as 'ee'.
Wikipedia shows the example of 'ysgrifennydd' (-nydd being the last syllable → 'ee'), which in 'ysgrifenyddes' turns into 'uh', no longer being the last syllable.
So the reason for the 'ee' sound in 'petryal' is obviously not the stress. I also thought that the reason may be because here 'y' is followed by a vowel, but my vocabulary is still insufficient for comparing other words with a similar feature.
Nadolig Llawen i chi hefyd (hoping this is correct).
Yes, perfectly correct about Nadolig Llawen.
The pronunciation of petryal is interesting. Something I never considered while I used it every day while teaching Maths for over 20 years.
One possible explanation may be the previous versions of the word were spelt 'petrual', which would have the correct sound. The Geiriadur Prifysgol contains examples going back hundreds of years.
Otherwise it could be one of the examples of the sound of the word changing because of the surrounding letters.