Difference between English and Spanish phonological systems
The fact that English and Spanish language use the Roman alphabet makes many learners believe that the same symbol used in two languages transmit an identical sound. Although there are some similar phonemes, these two phonological systems have lots of differences.
First difficulty which find Spanish learners of English is that the written and spoken language are very different things. There is a lack of correspondence between spelling and pronunciation, while in Spanish the pronunciation of words is directly represented by their written form. The number of sounds of these two languages is also different. There are 12 vowels in English and just 5 ones in Spanish. In last one there is no front-back opposition, no central vowels. It means that for native Spanish speakers the phoneme /ɑː/, /æ/ and /ʌ/ are perceived as Spanish /a/. The number of consonants is also different: 24 consonant phonemes in English and 20 ones in Spanish. Moreover, consonant sequences which are very common in English, for Spanish speakers present some complexity as the only consonant sequences which occur in their language are initial stop (/p/,/t/,/k/,/b/,/d/ and /g/) or /f/+/r/ or /l/.
Apart from the fact that English phonological system has more vowels, their length is important: still - steal, will - wheel, sin - seen. This words are minimal pairs with the differnce in one sound: /i/ - /i:/. In Spanish there is no distinction between long and short vowels, so there is a tendency to pronounce all these words identifically.
Another very important point which makes the speech in any language sound natural is a rhythm. English is a stress-timed language. It means that some words in the sentence are emphasized by extra effort: one of the syllables of the word are stressed. Stress syllables forms rhythm units. Other syllables in the sentence are unstressed. They are very short and are said very quickly, so they don’t influent to the length of the unit, in that way every unit has approximately the same length.
Spanish is a syllable-timed language, where each syllable has approximately the same length. Weak syllables influence to the length of the sentence the same way as the stress ones. For this reason Spanish learners of English tend to transfer their native rhythm to English. Special attention should be given to learning of this issue, as well as to pronounce in the right way unstressed syllables, which don’t occur in Spanish.