Interestingly enough, IPA actually does have a way of distinguishing these sounds. The Spanish t is always unaspirated [t]. But the English t can sometimes be unaspirated [t] as in "stamp" or aspirated [tʰ] as in "too"
That’s interesting, but the Spanish unaspirated t and the English one are different phonemes. The tongue is in a different position. If I forget and use the English t, my Spanish teacher stops me. The difference in sounds is quite obvious. So how, in IPA, do you spell the difference?
> but the Spanish unaspirated t and the English one are different phonemes. The tongue is in a different position.
That is not what "phoneme" means. They are different sounds, but they aren't different phonemes in either language; to be different phonemes, the same language would have to consider them different. Neither does -- in both cases, one is "/t/" and the other is "weird /t/".
Spanish <t> is dental, which requires the dental diacritic: [t̪]
However, since there is no alveolar [t] in Spanish, it will generally just be transcribed as /t/ rather than having to put the diacritic on all the time.
It's more complex. Spanish phonology dictates a denti-alveolar pronunciation of /t/, while typical English phonology (USA, England, etc.) uses purely alveolar /t/. So in Spanish, the tip of the tongue hits the back of the teeth, which doesn't happen in English. This distinction is not rendered in the IPA glyphs or any diacritic that I'm aware of.
I think it's not perfect, because (I believe) Spanish /t/ is usually denti-alveolar and not fully dental. I don't think there's a way to express that specific aspect of it, though I'm also not a linguist so I may be mistaken!
Aspiration is a separate phenomenon. English also has unaspirated plosives — they just mostly only occur in word-final positions, like the <t> in "pat", and they are not contrastive with their aspirated versions.
What I was talking about was how the Spanish /t/ has the tip of the tongue just a bit further forward, so that it touches the back of your teeth. English /t/ is, for most people, purely alveolar, so there's no teeth contact.
Agreed. But some Spanish speakers pronounce t with the tongue quite far forward, between the teeth; that’s what I meant by comparing it to an unaspirated English th. But I think we are getting into regional variations now.
It’s even more crucial with d. An English native speaker who is a beginner in Spanish will pronounce tened in a way that will be interpreted by Spanish speakers as tener.