
There are three rules which apply to every single vowel in Spanish, but first, do you like the picture? I made it myself. Let me make the introductions: readers, these are the Spanish vowel sounds, Spanish vowel sounds, these are the readers. Please notice the use of the words vowel sounds, which is something quite different from vowel letters. Both in English and Spanish we have five vowel letters, "a e i o u". With those five letters, in Spanish we produce five vowel sounds (the same happens in Greek, Hindi, Japanese and most Bantu languages). It really could not be simpler. It’s the opposite scenario for English, where, with those five letters, we produce the whooping amount of twelve vowel sounds. Even if English is your native tongue, it would be absolutely normal if you had no idea there where so many. In case you don’t believe me, let’s take a look at them.

/i:/ as in feel
/ɪ/ as in fill
/u:/ as in fool
/ʊ/ as in full
/ɒ/ as in lot
/ɔ:/ as in law
/e/ as in head
/ɜ:/ as in heard
/æ/ as in bad
/ɑ:/ as in hard
/ʌ/ as in love
/ə/ as in accept
Why is it important to know your English vowels? Well, in order to learn new sounds we have to compare them to sounds we already know, and figure out their differences and similarities. You can think of the Spanish vowel system as a simplified version of the English vowel system. In other words:
Spanish /i/ as in sí
In English you’ve got two sounds which resemble the Spanish /i/: /i:/ and /ɪ/. There are two main differences between those two sounds: the /i:/ as in feel is long, and the tongue is tense. The /ɪ/ as in fill is short, and the tongue is lax, it sounds a bit like the /e/ from bed, doesn’t it? The Spanish /i/ is a bit of a mixture: it is short, but the tongue is tense. Try to avoid that /e/ quality.
Spanish /u/ as in mucho
I could almost have copied the previous paragraph: the English /u:/ as in fool is long and tense, the English /ʊ/ as in full is short and lax. The Spanish /u/? Short and tense.
Spanish /o/ as in no
Again, in English we have two similar sounds, a long one, /ɔ:/, and a short one, /ɒ/. And again, the Spanish /o/ is somewhat short, but resembles the long /ɔ:/ regarding the position of the tongue. Also, consider this: have you ever heard that short /ɒ/ from lot in final open position (as in a word ending with a vowel)? I’m thinking you haven’t. Let’s consider the Spanish word no: think about it as a short /ɔ:/ sound. If you make it long, we’ll all know it’s not Spanish you’re speaking.
Spanish /e/ as in té
We could say it´s the same sound as the English /e/, but please, try to avoid that /ɜ:/ sound from heard, it´s way to long to sound Spanish (among other technical details rather hard to explain, the easiest of them being the part of the tongue that is raised, central for /ɜ:/ and front for /e/).
Spanish /a/ as in mamá
Now this one is hard. I’ve read the Spanish /a/ sounds a lot like the English /ɑ:/ from hard and father. This is not completely true: when producing the English /ɑ:/ we raise the back of our tongue, but when producing the Spanish /a/ we raise the central part of our tongue. Also, you have to avoid the /æ/ as in bad, because of that /e/ quality. The English /ə/ from accept should also be avoided, but that sound demands a title of it´s own.
English /ə/ as in accept, aka the schwa
This vowel sound does not exist in Spanish, and in English, it only occurs in unaccented syllables. That’s why it´s pretty common to use it in unaccented syllables in Spanish, but that is wrong. It´s the sound from alone, about, over, China (see how it´s never stressed). It´s a weak, lax vowel, it even disappears sometimes, we could just as normally say /lɪsən/ or /lɪsn/ for the word listen. This is something that never ever happens in Spanish. Every written vowel is going to have a vowel sound.
It’s a bit complicated, I know. But if you paid attention, you must have noticed some things which seem to happen to every vowel. That’s because there are three general rules which apply to every single Spanish vowel sound. Over the next days I’ll expand on each of these rules separately, but if you just can wait, you can start applying them right now:
1.- Spanish vowels are short
2.- Spanish vowels are pure
3.- Spanish vowels start differently from English vowels -and end differently as well!
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