Sounds and letters - two different things in English

The problem with English is pronunciation as the same association of letters does not mean necessarily the same sound. The problem is more with vowel sounds than consonant sounds.

Consider the following words with the same association of letters E+A and the different pronunciations: 

•  beat   <ea> is pronounced /i:/  
  
•  bear   <ea> is pronounced   / eə/   (and not beer /bɪə/)   
  
•  head   <ea> is pronounced   /e/  
  
•  near    <ear> is pronounced   /ɪə /    
•  heart   <ear> is pronounced   /ɑː /   (and not hurt /hɜːt)    
  

It can be even worse as the pronunciation of the word can change the meaning of the word:
e.g. row     /rəʊ/  - here row means "a line of seats"
       row    /raʊ/ - here row means "an argument, a disagreement, a dispute"
We call those words ‘homographs’ – which means: different words, written in the same way.

As there is no universal rule, learning a new word involves learning:

1.     the meaning
2.     the spelling
3.     and the pronunciation