Well I've now discovered how to replay sentences, and it is definitely a d, but with a BIG proviso:
d is not pronounced the same in Gaelic as it is in English. When you hear a sound you are not familiar with your brain will identify it as some other sound that you are familiar with. This sound here is unambiguously a d to me as I have been speaking Gaelic for some time, and it is easy to forget that it may sound completely different to other people. You need to learn and practise this sound, and get used to identifying it.
- Make an English th sound and notice where your tongue is, touching the top front teeth
- Now make the d with the tongue in the same place
- This is how you make both the d and t in Gaelic, both broad and slender
- I think this speaker may be sticking the tongue out past the the teeth, so it is actually the top of the tongue, not the tip, that is touching the teeth. Try it.
Is the method you have discovered right-clicking on the blue word in the sentence, or are there other methods?
This way I have found now several sentences containing fhalt. This one(A bheil d' fhalt glan? ) is somewhat more lispy than the others, while the sound of the other ones (e.g. Tha d' fhalt glan. ) is more like something between d and t.
So it is possible that I have heard a sound more akin to f for the first time (7 months ago), but have been more accustomed to the language now.
Yes, right clicking (more convenient than left, which also works) takes you to the list of sentences, which has the advantage, as you point out, that you can find all the sentences that contain the word. But is still not obvious why they don't simply have the button that they do in other languages, such as Welsh, to hear the sentence directly.
As for the voicing, this article not only explains, but also shows how confusing it can be. Gaelic is no exception, in loads of different ways, from t changing to d in the examples here from Lewis dialect (and see here), to words that are spelt with a voiced consonant pronounced unvoiced (sgioba usually pronounced /ˈskipə/) but given as as /sgʲibə/ in Am Faclair Beag to words that should be unvoiced according to the rules of Gaelic orthography (agus) * /ˈakəs/ but are in fact usually voiced /agəs/ and so on. So for this d' to go not just to /v/ but to unvoiced /f/ is not that odd. Specifically, this word is related to tu (unvoiced) also found in the French, Spanish and Welsh, which is usually thu (originally unvoiced /θu/) but is voiced in English thou /ðaʊ/ and German du /duː/ but then voices for the possessive in both Gaelic do and Welsh dy /də/. So it may not surprise you to know that it is quite often unvoiced in Gaelic. So /f/ instead of /v/ is not that surprising. What a shambles. D
Voiced and unvoiced consonants don't bother me that much. I have already got used to g/k, d/t, b/p etc. pronounced alternatively, or often as something in between.
(Another thing is to remember to pronounce it like that as well. As you have said before, when you hear an unfamiliar sound, your brain supplies the closest familiar one. It needs a conscious effort to overcome that.)
What is one of the most difficult things for me though, is aspiration. Not in clear cases, like mac pronounced as maxg. But those various weak puffs and lisps, like in the original example. I am getting better in understanding them, but trying to pronounce them feels rather unnatural to me.
It is great that the Duolingo course has a great variety of pronunciations, so one learns to understand various dialects. However, I'd like to know if some of the dialects have less aspiration and nasalisation, or if it rather comes down to individual speakers.